Most Mexican brick weed is sativa or sativa dom. I got a nice chuckle reading this thread and some of the answers. Yes you may get some shitty mexican and you might get some surprisingly good brick (not as often as in years past). If you were to take the time to investigate this subject through a seed search engine, I will enclose a link for you, you will find that most of today's strains which have any sativa in it has its roots in mexico, columbia or other central american countries, last but certainly not least is Thai.
Most of the brick weed was ruined in the 80's with the introduction of indica to the native lines in order to obtain more weight and shorter flowering times. Some of the old landrace variety sativas can flower up to 26 weeks and are harvested in Jan and Feb. these long flowering types most of which still flower 12 to 18 weeks outside are very potent but also very hard to find. Living in Central America and traveling around, been living here for almost 5 years now, I still find excellent brick weed coming from Panama and Columbia.
In parting I will say I don't look for brickweed, but at least down here I always try it when I run across, and when its good I am first in line asking my host or amigo "tienes semillas?", translation Have any seeds?