1- how can I draw different map limits? 

For example draw a path around Los Angeles and another one around San Francisco, so if a user is GPS located inside LA, then a list or some information can be loaded relating to LA and a POI can appear with the directions to there.

2 - the tricky part also is that even if a user is nearer to a POI but he is not in that delimited zone, the POI related to that zone is the one that should appear to him so as that information.

Thanks for your support