I will be in Palma, Mallorca for 2 or 3 nights in August and would like to go to one of the famous beaches such as Es Trenc. Is renting a car the only option?

Thanks,
Glenda

The train system is very limited on the island and doesn't have a full coverage. I have no idea about the local bus system but the roads to Es Trenc are all good quality and even in August, will be fairly quiet, just the town of Campos which can get busy.

When you're in Palma visit the cathedral and Bar Abaco for very different reasons!

For a short stay, it may be worth considering taking the old tram/ train over the mountains to Soller. The journey has a beautiful route and Soller is beautiful town.

There are of course buses between Palma and Colonia Sant Jordi, a place close to Es Trenc
https://www.tib.org/en/web/ctm/autobus/linia/502

Thanks. I was thinking of renting a car but it looks like the options are all stick shift (haven't driven one in many years). I might try the bus to Colonia Sant Jordi. However, it looks like a long walk to Es Trenc. Are cabs or uber available from that location?

Thanks again!

"Are cabs or uber available from that location?"
May be. But the itinerary via the hinterland would be 3times longer. Along the beach (only on foot) it's about 1 mile.