With Hilton Brands you can earn both miles and HHonors points. Since you are staying at the hotels, you might as well sign up. Hilton's program lets you choose how you earn:
• HHonors Points and Variable Miles
Earn 10 HHonors Base points + 1 airline mile per eligible U.S. dollar spent*
• HHonors Points and Fixed Miles
Earn 10 HHonors Base points per eligible U.S. dollar spent + 500 miles per stay (100 miles per stay at Hampton Inn, Hampton Inn & Suites, Homewood Suites by Hilton**, and Scandic hotels)
• HHonors Points and HHonors Points
Earn 10 HHonors Base points + 5 bonus points per eligible U.S. dollar spent

You need to figure out how you will spend which option makes the most sense for you. I'm guessing, since you are saying you won't be staying at a lot of hotels, that one of the 1st two options will be best. Go to http://hhonors.hilton.com to find the best way for you to earn.

The conversion rate for HH points to AAdvantage miles is 10,000 points = 1,500 miles. All the details are on Hilton's website