Thank you so much for the advice above. Although from 2010 it was still very useful! We managed to get to Punta Hermosa with your tips by the same idea: make your way to the Carretera Panamericana Sur (the big high way) and then take a bus to Punta Hermosa. We did choose a different bridge though, Puente Benavides. The advantage is that this bridge is close to Universidad Ricardo Palma, which every combi driver knows
Also, we started in Miraflores.
The next challenge was finding surfboards, as Punta Hermosa is a bit of a ghost town in low season. So if you want to rent these, it would be smart to go to Bravo surf camp! To make it a bit easier to follow, we made a blog post with google map locations and photos: https://www.travelswellspent.com/punta-hermosa-by-public-transport/
Hopefully, this helps!