In Cabo you can go to J&J Habanos, they are authentic and this is a great shop, very nice walk-in humidor. Very friendly people, great selection. The owner also have another store in town called something else, but I've never been there. There are a few others, but this place is the real deal and highly recommended.
In PV, I would highly caution buying from anywhere but the La Casa Del Habano shop, I have never seen so many fakes, there are full stores of them. I was in one shop that had Monte Petite Edmundos for two different prices in the 3 pack tubo sets. The lady told me one was fake the other wasn't...be cautioned here and most places for that matter, a lot of fakes. The LCDH store has a nice lounge downstairs where you can smoke and a very small selection IMHO for a LCDH store, but they are real.
Anyway, in those two cities, J&J and LCDH, other places I would be cautious...