Hi,
as you didn't mention, where exactly you will go, I cannot to recommend a diving center, but most centers offer guided dives in groups, and a properly working diving school will anyway guide their beginners until they have a certain experience to dive with a buddy on their own responsibility.
To find a diving center in the region of your destination, go on the pages of our Mexico Guide,
Mexico diving centers - GoodDive.com
There you find a list sorted by regions, which can help you to choose a center that fits to your expectations.
Have a nice holiday!
Geli