Lots of the area around Casper is loaded with goats, and there is a good bit of public land, as well. Areas 62 and 63 are good ones, as are the areas along the Shoshoni Hwy (Hwy 20-26 out of Casper). Lots of flat land, but lots of hilly terrain, too, so spot and stalk is a possibility, but take it from one who knows, stalking antelope is an exercise in futility most of the time. Hunting waterholes is much more productive, but spot and stalk is a hoot.
Get some BLM maps of prospective areas that will give you an idea of the terrain, or do the Google Earth thing to see what the area looks like. Early season antelope weather can be 90 degrees or snow, depending. And you might want to plan around the rut, which has been going on for about two weeks now. The bucks have the ladies on their minds, but are herded up, so there are lots of eyes to see you.