It's not that hard to survive in Los Santos- RC, WV and FC are all very difficult because there isn't much to hide behind and in. People survive doing really weird shit in LS, like jumping from the tallest building down to a camping spot, taking over the ship in the southeast corner of the map, and by not camping at all. Part of the fun is finding new camping spots- many of the old ones have been forgotten. For example, have you tried parachuting down to the lighthouse near the beach? It's a very nice spot. Have you tried the city hall? Have you tried taking over the pier area that Crash suggested? There is only one way in, and plenty of buildings to run around and hide in.
Don't forget that driving, flying and stunting can also be used to survive, and in LS I think they can be much more effective.