Upvote:6
I was reluctant to put this as an answer as I don't have first hand experience or any official sources, however yes I believe it's allowed.
You are almost certain to be stopped and questioned about why you're towing a vehicle into Mexico. Many do this with non-running vehicles and there are requirements that must be met to be allowed to do this. I realise that this isn't what you are attempting, but you may be asked to prove that the vehicle is in working order and explain the purpose. People do this all the time, often with off-road cars (eg Baja 1000 type races).
In my opinion, it would be much much quicker to have the two vehicles driven separately by different drivers. It might even still be quicker for you to drive one in, walk back across the border, and drive the other in, versus the time it takes to go through the questioning when towing. I might be wrong and maybe there will be no questions, but I feel that's unlikely