I am planning to apply for 2-3 cards to get some hotel loyalty points.

I want to book hotel nights in South America ( Peru, Chile, Argentina - thanks to 100K BA miles )

I have never had any hotel cards before.

Chase Saphire Preferred

+1 good card plus 50k bonus to start

I have the Chase Saphire Preferred, I was hoping to get some other cards as well need to book 10+ nights

Look at the first Sticky in this forum. It has a list of HOT credit cards. There are two Hilton cards that will give you up to 110K points.

My wife & I both have the Chase Marriott 70k each + 1 free nite

I have the Marriott premier visa card as well as the priority club visa. Many people like the Starwood Amex. I prefer to stay in Marriott's. There's a good bonus on the card currently. The other benefits are 1 elite night credit for each 3k spent, a free night at a category 1-5 hotel each year, 5X points on Marriott stays, etc. I have the PC card because the free night they give you is only limited to hotels where they sell rooms for points, not category limitations. So you can use the free night at most hotels in the priority club program. I'll probably use my free night in NYC in 2012. There's also a good bonus in place forthe PC card.

Starwood Amex is another good card, for general purpose use if not for the sign up bonus. One can easily get 4-5 cents per point by redeeming them for SPG cash+points stays.

The VS AMEX card has a 50k signup bonus which transfers to 100k Hhonors points. I value those miles too much to transfer to HH but others have reported success.

You are going about this backwards.

Figure out what hotels exist in the areas you want to visit. For example, Hyatt, a good place to transfer Sapphire points, has a limited footprint.

Then look at CCs that will yield points in those programs.

And I would add that it is good to amass points in a number of programs. When you go to a city, if you have enough points in a few good programs, you'll be able to choose the hotel that best suits your needs. Tripadvisor + several reward options = happy.

Chase Sapphire can be an option here as you can transfer instantly to hotel programs as needed. But don't neglect the opportunities when they arise; e.g., the Marriott card a few months ago that offered 70k + 1 night for no minimum spend.

And the Marriott card gives double points for airline purchases and dining.

Chase Sapphire preferred seems like the best.. 50k points that can transfer to hyatt or marriott. Plus the freedom card points can be folded into the UR balance. Otherwise I am wanting the SPG and Marriott cards, but I do not know If I could keep all three after capturing reward points

Wait a second. Where in Peru, Chile, and Argentina???
Have you looked into which hotel programs even exist in the places you want to go?

You may be suprised as to how little choices you have, unless you're only going to the huge capital city in each country.

For example, in Argentina, if you go to Salta (in the northwest), there's only one chain hotel, Sheraton (part of SPG). If you go to Iguazu Falls (Argentinian side), there's again only a Sheraton as far a chains, but in this case even on points its very expensive (the signup + spend bonus for the SPG Amex card will not even get you two nights there!). Go to the tourist towns in Patagonia that have a chain hotel at all, and it's likely to only be a Howard Johnson (part of WyndhamRewards), but WyndhamRewards is a program where you don't get very much from a sign-up bonus (not even enough for one night in South America!). The only good way to get WyndhamRewards points is to start using them for cheap US suburban motel stays during promos, but even that will take a year or two to build up enough for a few nights in Patagonia, since each promo is tightly capped.

On the other hand, also look into the exchange rates, and how much it costs to get hotels for actual money (in which case you do not need to limit yourself to chain hotels). It may turn out that in some of these places it's not even worth it to consider using points necessarily.

Indeed, but that only works at certain category hotels (and even then it's not always available). The OP wants to go to Argentina, Chile, and Peru (but hasn't yet explained where in each of those countries).

In Argentina, a small number of SPG points can go a long way at Sheraton Salta because cash+points is available there and a fantastic value. But there's no cash+points at Sheraton Iguazu Falls Resort, and it's mighty expensive on points too (12000 to 16000 points a night, depending on season), so it can drain an SPG signup bonus in no time at all. (I stayed there multiple nights -- during the 16000 points/night season -- using free night certs earn during a promo last summer. I couldn't have afforded it any other way.)