There are 2 filter buttons. First one is for the critter based and the second one is for the type based. They are two different functions and has nothing to do with each other.I made a picture to help understanding this:http://img265.imageshack.us/img265/4752/helpim.jpg
It is pretty slow on IE but yay me for high IE performance computer/internet connection .
I found out that BH Caravans come can be found on the square to very right of New Reno btw.
Caravans can be found anywhere, as they are caravans and all the time move