Cheap, On the Beach Hotel?

Or the Tropicana if you can get over needing an AI.
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Vaporizer Wiki

I think you will find something up in Nuevo. The beaches are nice up there, and you will find many AI resorts to choose from. For what you hope to spend, I think you could land a pretty good deal.

We have stayed at Paradise Village up there and would recommend it if that fits into your budget.

If you are looking for clear blue water and gorgeous beaches, you might search a little on the other side of Mexico. Different terrain, Caribbean clear blue water and AI hotels if that is what you want. Many will be open soon and I think some are open now. Certainly not as much going on as in PV and the food choices are not as diverse, but the water and beaches are gorgeous!!

good suggestion above. what you describe really does sound more like the caribbean side of the country.
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NO2 VAPORIZERS

Just thought I would add that the Decameron Los Cocos is a different resort from the Royal Decameron. The Los Cocos is quite a bit farther from PV proper I believe. However, the Royal Decameron is in between Nuevo Vallarta and Bucerias and is a lot closer to PV.

You can usually find last minute seat sales to the RD.