I've tried several. I even run my own as I rent a server in the US so I can easily setup my own VPN. Mine works fine for Pandora and various other services. I can't get mine to work with US Netflix because Netflix is ridiculously aggressive about detecting VPNs and my server is on a well known IP block of rented servers.
For me, the only one that has reliably worked to watch US Netflix (if that is important to you) is ExpressVPN.
As far as using VPN for privacy... privacy from whom? If from Movistar, sure, a VPN will do the trick. It'll can also work to hide yourself from casual searches or investigations, as long as you take reasonable care, but you have to clear your cookies and cache often. Amazon and Google are quite clever in their methods at tracking even people who use VPNs.
If you're trying to hide from the FBI or NSA, though, good luck with that. Unless you're super careful all the time you're bound to slip up an unmask yourself at some point. You basically need to be an expert IT professional to pull this off, and even then there's no guarantee.