The 2 resorts are joined so the walk won't take you that long. We stayed in Cala n Blanes and used to go into Forcat for our evenings out. The beach in Cala n Blanes isn't that big so might get crowded - depending when you are going.
The little train runs up until the early evening.
There's more bars/restaurants in Cala n Forcat plus small supermarkets. If you want some serious shopping the pop into Ciutadella on the bus - it's not far but there again nowhere's far in Menorca really.
Menorca's a very laid back Island & is very family orientated, we never saw groups of teenagers etc for instance. If you want a nice, chilled out, quiet holiday then Menorca is ideal.