Did you just recently start having issues or has this always been an issue? What does Sprint.com/coverage show for your location you're having the issues at? There could be a number of different causes for losing signal, if you post your zip code I can check to see if there's any current outages listed. Are you the only one having issues or do you know someone else with Sprint having same issues?
This is actually a very common problem for the new samsung galaxy s2. Everyone I know has a problem with 3g, 4g, and cellular service constantly going in and out. Supposidly there is a patch that android is working on to fix this for our phone. This is pretty frustrating and I live in the new york city area.
I have a LoS problem with my Galaxy S2 Epic. The phone will either show a 0 with a strike through it or show bars for phone service but not service. I also have had the phone just cut out while I am on a call and then the phone freezes up and will not hang up the call. I hope this gets resolved because I pay way too much for this service not to be working and I use the phone for work. Time is Money Sprint get it fixed!!!!!!
Have you been prompted for the software update yet? If not there is a software update which will address the issues you're experiencing. Click here for more information. Also, it's always a good idea when changing or updating any software to backup your information first, there are several applications on the market that will allow you to backup contacts, applications, text, etc.