One of the best ways to protect a laptop is to make it look like you don't have it with you. What has worked for me when carrying valuables has been getting an ugly bag from a local market. If you walk near the larger produce you should be able to get an empty bag of flour or whatever for 2q. It may be dirty outside but very clean inside. No one is going to empty a bag of flour without getting every last speck out of it. Put your laptop in a bag like this. Oso blanco is my favorite. Then put something around the laptop like a sweatshirt or whatever. Then, you can act like you don't have anything valuable but still keep your eye on it. You can casually put it on your laptop if you are on a bus or shuttle but don't bear hug it with two arms unless you want to tell everyone that you have something valuable. Not wearing expensive jewelry, expensive clothes, etc. can also help lessen the attention.
Having said that, I have seen many people flash around all kinds of iphones, ipads, etc., while talking loudly about needing to get money out of the ATM. Luckily, most of them finish their trip with no major problems.
