Hey Bruce,
I'm suporting and teaching one new rebreather facility and IANTD training facility in Guadalajara trough Protec. They have plans to open one store in Vallarta but will take a while. For now they have Extend Air for sell, 4 O2ptimas and 13cf Al tanks for rent.
If you need 02 they are working together with the Scubapro dealer in Mexico, his address is
www.vallartech.com or you can contact Pedro MR, the guy start this thread; he is marine biologist and work with them. They can supply 02, stages, private boat and great service. Even if you need rent tanks from Azul Sin Limites, the rebreather training facility, they take care for you.
If you need any advice on that area or in La Paz area just send a e-mail or PM.