The Garmin eTrex Venture HC that I use does not have a lot of bells and whistles, but works great for geocaching. It has a high sensitivity receiver, USB, color screen, "geocaching mode", decent battery life, and takes AA batteries. Together with a case and NiMH batteries it'll still come in below $150. I bought mine for $115 but Amazon has since raised the price to $130.
Check out the Delorme PN-20 at www.delorme.com. It is a little more money that you stated you wanted to spend, but you will be glad you spent the extra if you can. It comes with Delorme's Topo 7 map package and is a great little unit. You will be glad you got the map program and the extra functionality.