We're spending our first night of vacation on Isla Mujeres before heading down to Puerto Morelos. What are our chances of getting a room on the spot at an inexpensive small hotel without having a reservation? The Hotel Belmar wanted my credit card info via email, which I'm not comfortable with. Any suggestions would be great! I've been obsessively reading the forums and can't wait to go! Going 4/9/10-4/17/10.