Haha that'll work. The activities on Coz are pretty spread out along the channel for many miles so it's hard to avoid using a cab or rental car if you want to go someplace different. VB is not an excessive walk from town, but we were too lazy for the 70 peso cab ride. With several cafes and a convenience store within a block tho, you can minimize that.
That $10 map will help a lot.
From that map, it looks to be about 5 miles between Villablanca and Scuba Club Cozumel. I guess that means a taxi if I want to scope out the competition.