Hi there, sorry I can't talk about the Palladium as I,ve never been there, but I just returned from the Melia and can answer some of your ??.
Timeshare vendors- the trick is to answer "yes" when they stop and ask you "have you received your gift yet?". some are stationed at the entrance to the beachside restaurants. They are not pushy, so just say "not interested".
Food- General run of the mill fare. We ate every night at Los Atabales, which is the general no reservations needed buffet rest. We couldn't get reservations for any of the themed restaurants- but hten again we were a party of 10. We heard complaints of people not getting reservations eve with 48 hours notice (I guess they didn't grease any palms

).
Pools- both pools are HUGE and have swim-up bars. Presidente is the on-tap variety which I don't care for much. Piña colaladas/Daiquiris are slushie types from a machine. They DO have mamajuana if you ask for it.
Nightlife- there was live Latin music in the lobby of the Tropical with people dancing. In the Caribe lobby there was just the bar. There's also a lounge of sorts with canned music between the Caribe and the Tropical. I believe these close around midnight and you're invited to go into a pub just off the Tropical lobby which is open til 2 am. Also, the casino bar/lounge is open til 3 am.
Beach- was not rough, but itwasnt Boca Chica either. Sand was kept fairly clean (no kelp/seaweed).
Hope this helps, enjoy your stay!
E.