Ella -

I'd assume that the horse riding you've done was with "English tack."

In the Texas cow country they use a 40 pound saddle that's like sitting in a rocking chair. You'll want to try it, just to see what a comfort it is.

And don't worry too much about the tarantulas. They don't come out much in the heat of the day. But I'm surprised noone mentioned the several kinds of sandburs.

John