Local taxis are readily available and will know where the theatre is located, and are roughly priced at €6 from Magaluf, €8 from Palma Nova, €14 from Santa Ponca one way. There is a taxi rank directly opposite the theatre on Cami Porrassa. You can make a booking with Calvia Taxis here: https://taxiscalvia.com/reservas
Resorts closer to the theatre (Santa Ponca, Palma Nova and surrounding areas) are easily accessible by local public transport, with a bus stop immediately outside that serves the bus routes 123 (Santa Ponça – Cas Català) and 104 (Magaluf – Palma)
If you are driving to the theatre, there is free and ample parking outside, the venue is accessible via the Ma-1 motorway, taking exit. 14 (Magaluf / El Toro) then over the roundabout onto Carretera Cala Figuera, continuing to the third roundabout marked with an 8. Take the second exit down Cami Porrasa on to the roundabout opposite Pirates Theatre.