If you are worried about the number of times you can enter on a visa waiver, don't - I have entered the USA 50+ times on a waiver and the guys at immigration ask me how I am going and wave me on each time.
This was even more fun before they closed 'The Mexican Loophole', where you could drop out to Mexico for the weekend and get a new visa on the way in. I had a lot of fun weekends in Mexico before they shut that down. You now need to leave the North American continent (they included Central America when people started flying to Belize to get new US entry visa's)