Funny how these threads often devolve into arguments and insults...
Honestly I never book either of the two ethnicities requested by the OP, but Lear has slew of latinas and occasional blacks.
Currently Lear has 7 latinas on the roster.
MBV has many latinas as well. And they had some black caribbean girl last week.
And BDJ is almost solely a brazilian girl agency now.
So there you go. Three well reviewed agencies to pick from. You'll need solid references though. Good luck.
BTW, SA = seeking arrangements (seeking.com).