Is it safe for single woman to drive to Mexico?

The U.S. State Department has warnings for specific areas:
https://travel.state.gov/content/passports/en/alertswarnings/mexico-travel-warning.html

In general, avoid traveling in the countryside at night.

Make sure you have the proper insurance and other documents for bringing a car into Mexico.

You should familiarize yourself with Spanish you might see on Mexican road signs:
http://www.ontheroadin.com/mexican_road_sign_translations_f.htm

Well you're not just driving to Mexico, you plan to drive around in Mexico for 6 months if I understood correctly.
That means you'll have to deal with all the hassles of car ownership in that country in addition to the safety issues, the bigger safety issue is not armed gangs, but you not knowing how Mexicans drive. I don't remember Mexico, but for example in Peru, the way people drive is vicious, I would be scared to drive there. I would definitely do an exploratory trip first, and consult some expat forums, they will give you better answers than here. Once you get outside the US, car issues become much more difficult.

To get to Puerto Vallarta, wouldn't the route go down the coast through SInaloa, where those two Australian surfers were murdered and their van torched (in 2015?)? I was driving around in Baja at the time and they had taken the ferry across to the mainland. Has the situation changed radically in the interim? Would it be realistic to have some caution about driving alone in that area?

I have driven in Mexico but I use Mexican rental cars and I can speak
Spanish . Having a dog a problem as most places will not rent to you. I would say board your dog and fly down and get to know the area first before attempting to do this drive. My sister and her husband drove down one time but they were held up and their suv stolen. I suggest if you do this to have full insurance o everything including yourself for this trip

I am planning at the end of the month to drive from Edmonton to Puerta Vallarta.

Okay, I've heard a lot of complaints about Canadian winters, but is the summer weather there bad too?

...she would never drive as the border crossing is unsafe.

I suggest to you that it isn't specifically the border crossing; it's northern Mexico specifically, and Mexico generally, if you're unprepared.

I am more concerned about the armed checkpoints...

I have faced many armed checkpoints and never found any to be a problem.

...really want my car to be able to get around all of the things I want to see in Mexico.

Public transport is very good in Mexico, much better than Canada. But your dog will have to go in a luggage container.

LOL I am actually from Vancouver Island but am driving to Edmonton to visit my son and his gf before I leave.

Going down before hand won't work in my situation. My husband and I are separating, have sold the house and we are both leaving on the 20th. He's going to Ontario with our other 2 dogs and the other one is with me. Boarding her for 6 months is not an option in any way. I have found many places to choose from which will rent to me even with a dog. I do have a contact in PV as well as one in Isla Mujeres. The other reason I wanted my car is that I am also undecided between PV and Mujeres. I have rental offers at both. My intentions were to stick to the toll roads and no travelling anywhere near dark ever. I also wanted to meander through the States on my way back on January or if I really love it there just turn around at the border and get another 180 visa. I see the car as giving me more freedom than if I just flew there :s

Edited to add: I am insured up to the hilt and my car would be as well.

Also edited to add lol I think part of the problem is that in Canada we have this idea that Americans just drive over to Mexico all the time. You know it's in the movies and stuff :P

Check out the Facebook page "On the Road in Mexico." This question gets asked and answered there all the time. There are hundreds of people from the US and Canada sharing their experiences driving into and through Mexico, including solo women and their pets. A LOT of them drive to PV. Make sure you are also aware of the new regulations for bringing dogs into the country (proof of vaccination against rabies and distemper, administered at least 15 days before your pet enters Mexico, and international certificate of good health within 10 days of travel.) Please report back if you decide to do this! For Spanish, you could start with an online program using Duolingo or get a Skype tutor on iTalki (which is wonderful and cheap.)

Edited to add: I am insured up to the hilt and my car would be as well.

That means nothing since any car insurance from north of the border to Mexico is null and void. You MUST buy Mexican car in insurance, which I suggest you do online.
I have been buying my car insurance from San Xavier Mexican Insurance for many years. There are others i.e Sanborn, very expensive, Lewis and Lewis also very expensive. I pay about US $ 350.00 @ 6 months FULL coverage for a 2015 vehicle.
Since you are from BC, Save gas and hotel etc receipts to prove when you're away since you will get your BC insurance premiums deducted while you are away.
Each and every insurance company selling Mexican insurance resells from about 5-6 different Mexican insurers.

As for safety, ignore all the NAY Sayers. Some of them have never been to Mexico. I have driven to Mexico since 2002 and have never had any problems.FMT (180 day permit) and your TIP which is your car permit. The TIP cost depends on the age of the car. Both can be paid by credit card. You will also have to pay for a few photo copies there and then.

Mexican drivers are just like you may be used to, except on straight highways the go like a bat out of hell. Mexicans generally are bad on curvy roads. When they are driving a slower vehicle. many times they;ll pull over to the shoulder to let you pass. I drive as many toll roads as are on my route from Laredo to Manzanillo, Jalisco. It may cost me about $ 120.00 but it is safer in the sense that all villages, cities and towns in Mexico have dozens of ( Topes) speed bumps and if you miss one driving fast it may wreck your front end necessitating an expensive repair.

Driving in Mexico on smaller highways to make a left turn you pull over to the shoulder on the right and let all traffic pass before you make your left turn. In many larger towns and cities they have the main road and the lateral road. In those cases you must be on the lateral road to make turns, left or right. As you are driving along the vehicle in front of you may put on the left turn signal which can mean two things. They ARE turning left or they are telling you to pass since they think it's safe to pass. BE CAUTIOUS !

Signs along highways can be confusing to someone not familiar with Spanish. On my first drive it drove me nuts since I was on a toll road with a 110Km/h and suddenly there is a sign 30 Km/h. It took me a while to realize these signs were meant for an exit. Signage on Mexican highways is not as good as it is up north. You will see signs such as "Curva Peligroso" which means a dangerous curve. "Velocidad" = speed. "Alto" is a stop sign. In towns and cities you stop when it says ALTO, the small town where I live in the winter ALTO is usually ignored.
When driving in small towns and villages be careful, Mexicans will shoot out of a side street seemingly without looking.

I'd also suggest you have an "UNLOCKED" cell phone and in Mexico you buy a TELCEL SIM ( called CHIP) card. Telcel has excellent coverage all over Mexico. I pay monthly about 300 peos which gives me 21 days of phone calls all over Mexico and phone calls up north for NO long distance charge. It also includes about 300 MB of internet for emails. This is also good for when you drive back home within the USA and Canada for phone calls.

Read this for some more info about driving in Mexico

More about driving in Mexico

About Mexican safety

THANK YOU so much for the facebook group! I have only been able to find men and couples who have driven so this is SUPER helpful!!

I should have stated that for car insurance I was planning to go with Great American El Aguila
Extended Coverage. I got this link to all the road signs which I was planning on printing out but admit it will be difficult as it is so long!!
http://www.ontheroadin.com/mexican_road_sign_translations_f.htm

Thank you for the cell phone tip. I was planning on looking for a sim card as my cell providers rates for mexico are ridiculous. I got one when I went to Nepal and was shocked at how little I actually used compared to at home.

Honestly getting the dogs stuff ready and set up was the easiest part of this plan lol