Other Hotel Programs - Sol Melia MAS program

Just a few words about this very popular hotel chain (in Spain mainly). With some business in Spain, I (hardly) gained 2 free nights in a Tryp hotel (midrange). I booked at the Tryp Menfis in the overpricey Madrid (nicely renovated, on the Gran Via in the City center). Breakfast for 2 was free (and great), no taxes, no nothing! Very nice award memories.

The Sol Melia web site seems to show that the program is free to join, and that its members get free breakfast on any paid rate. Sounds great.
Does anyone know if this is true? Also, do you have to book via the website, or can you book on Expedia, etc?
Thanks for any feedback!