We are new to the island as well. We had planned to go down in January to buy, but found something with our realtor that we couldn't wait on, so we've already bought it. We still plan to go down in January, but now the stress is off for the looking and we'll have more time to enjoy the island and concentrate on the remaining construction on our unit.
As far as advice goes, you should consider if you want to be in town, just outside of town, or far off in a secluded area. We liked being walking distance from town, and so wound up just North of the bridge. We felt the location was the most important factor, and this met what we were looking for.
Since we are new to this forum, I'm not sure if we are supposed to list agents and developers. But you can PM me and I'd be happy to point you to who we worked with. They were both extremely helpful.
Out of curiosity, why did you sell your place in Cozumel??