it does work.. :)
I also live in LA and have an lg thrive and same plan i pay 75 a month.. and i was just in tijuana but i put 100 bucks on my phone. And as i was going by car and when i got to otay mesa i was still in the US side and i was just minutes away from the border my phone said no service i completly lost service from at&t. I was all freaking out thinking it wasnt gonna work because my boyfriends droid razr on verizon had already connected to a mexican network and his verizon razr said "Roaming" in the screen i was all pissed of and stuff but to my surprise as i was getting closer to the border "Telcel gsm" kicked in and i got a 3G icon and full bars and a message saying i was out of at&ts coverage area and roaming on a mexican carrier.. once i was in downtown tj i made a few test calls back to the US and called local mexican numbers on my lg thrive while roaming on TELCEL and everything worked fine they DID charge 25 cents the minute so thats awesome!! Compared to $1.99 the minute on my boyfriends verizon droid razr which by the way also worked fine no problems either in verizon.. only difference his roamed on another carrier called "iusacell" but same thing it worked only differece they charged him more.. o also i noticed at&t has better roaming agreements than verizon cuz i had 3G everywhere i went in tj while verizon only gets a 1x , or 1G icon it dont even get 3G lol how laaame..