Struggled to find simple hotel in Merida a couple of years back, so in the end stayed in the Parador. Fantastic place. Safe underground carpark. Merida itself is a little gem. Theatre, circus and amphitheatre. Also a moorish castle. I think the museum is closed on Mondays or ir might have been a national holiday when we were there, but it's a great reason to go back. If you find somewhere reasonable could you post it up.