The map generator places wonders after it chooses starting locations and won't place one within 5 tiles of a start location. On deity, the AI only needs 100 faith for that first GP. I'm not sure if they need half faith for the pantheon too.
I'm fairly sure that the AI would not work Mt. Sinai in a size 1 city.
Meeting 2 religious CS will get you a quick pantheon, I don't think you'd have much chance at getting that before 3 forest Celts but it's pretty plausible to beat 1 forest Celts.