Yesterday I was at a place I rarely ever visit. Actually, I was surprised Sprint had coverage in Rincon, since it's a tiny beach town in western Puerto Rico. My iPhone 4 had almost a full signal with 3G; however, my husband's phone, a Samsung Galaxy S II had either no signal or constantly told him he was about to go into roaming and whatnot. I was posting pictures to Facebook and sending MMS to my mom and he was stuck with a very expensive dummy phone. My brother-in-law was there too and he has an LG Optimus V with Virgin Mobile and he had almost a full signal with 3G. Two very different phones connected to the same network working perfectly fine means the issue was not with Sprint.
I believe there must be some sort of issue with the Galaxy phone. I would like to know if someone else has had this same issue.
Since where I live, signal quality was only bad in my house that was on the outskirts of the city and pretty good inside the city, we decided to use a Sprint program called the AiRave (http://now.sprint.com/airave/?ECID=vanity:airaveaccesspoint). It works by hooking up to your internet service at home and boosts the signal for your phones inside your home. So far, our call quality has vastly improved and best of all, it's completely free to get. I hope this helps everyone. Overall, the phone's signal quality issue outdoors or in the city isn't bad for us, but it was really terrible in our home.