How safe is travel in Merida and the Yucatan generally? (I have read that all big cities in Mexico have problems and even tourist areas are becoming sketchy.) We are flying into Cancun and thinking of spending a few days in Merida and then going to Progresso or one of the other fishing villages, as well as visiting some of the ruins. Is it advisable to rent a car or is public transportation fine? If renting a car, is it ok to take small back roads as opposed to toll roads? Thanks for your help.