To access the dunes and the beach, you can go through the Maspalomas lighthouse (El Faro) or the Riu Palace (large white building) at the foot of Avenida de Tirajana.
You can visit the Lighthouse taking a taxi (ask "faro de Maspalomas"). Lighthouse, join and walk along the beach to the cottage number 7. This is the gay and nudist beach, you'll see a floating gay flag