Weather, it's going to depend on if you're in or near Buffalo. If you'll be in the Bighorn's there might be some snow. It'll be in the low 20's at night and maybe hit the 60's? It all depends, last year it was pretty warm that first weekend in October. Expect a lot of wind, great for spot and stalking, buy a cow decoy...they're worth it.
I think there's some good HMA and BLM west of i-25 in unit 20. You'll find some antelope in the mid 60's to low 80's if you're lucky. Unit 22 there's some large antelope but very little public access and most landowners make you pay a trespass fee of $250-600. Lots of great Mulies in/near the bighorns just have to find them.