Overland from Texas to Nicaragua

I don't think it's a silly question, I just think it's silly to post in (only) on the USA board. If you know where in Texas you're starting from, somebody here may have some thoughts on the drive from there to the border, but from there on you'll want to ask at the Mexico and Central America branches.

For the Mexico part of the trip, be sure to check out "The People's Guide to Mexico". Incredible amounts of information about driving in Mexico.

While you're posting elsewhere, you might also want to indicate whether you will dirve or take public transit. Different tips for different methods.

A major concern is US immigrations.

If you are eligible and plan on using the VWP, you may have issues if you don't have an onward ticket departing within 90 days of your entry into the US. Issues such as, the airline not letting you board at home, or being denied entry to the US if they do.
If you get a visa, you won't have to worry about the onward ticket.
You must also remember to turn in your forms at the Mexican border.

I'll admit, I didn't bother looking.

I doubt "Natasha" is a "he." ;)

OP's profile gives his country as Vietnam. If that's his nationality, he won't qualify for the VWP.

If you know where in Texas you're starting from

Looking at the prior posts, it's Dallas, after a stop in Iowa City for homecoming weekend with the Hawkeyes. On a nearly-expired Australian passport.

This is a strange collection of destinations, to say the least.

OP, Greyhound, which you've already found and apparently already plan to use on the Iowa-Texas leg, is affiliated with companies that run buses in Mexico. You transfer in one of the Texas border towns (Laredo, El Paso, Brownsville, or McAllen) to a Mexican bus. I've never attempted this, because I personally find bus travel tedious and uncomfortable literally to the point of nausea for all distances beyond about 100 miles, so I can't give you more information than I can find on the web.

South of Mexico, I have no suggestions whatsoever.

--M.

#5 -- And I didn't go past the summary bit. Australian living in Vietnam.

bzookaj is right that you'll want to get a visa, OP, which will probably mean a trip to Hanoi, if you're not already there.

I know to some of you this might seem like a really silly question,

I don't see a "question" in this post at all.

As for the request for "input," I suggest the OP read the first post of the FAQ, paying special attention to points #1 and #3, then try again.

If he continues on through Panama he can take a troll bridge over the Darian Gap.