There are apparently 4 cab firms operating in Menorca today.
It is now possible to ask a bar to call you a cab.
Santa Monica is situated on Cami de Talis (which leads to a remote beach between Son Bou and Santo Tomas that is now cut off on the main road but can be approached along the cost). Cami de Talis is an old track leading from Es Migjorn Gran down to the coast.
There is the Asociacion Menorquina de Radio taxi
Centro +34 871 52 00 70
Ponent (Ciutadella end) +34 971 48 22 22
Llevant (Mahon) + 34 971 36 71 11
Then Taxi Menorca
+34 871 52 00 70