Did you mean the jw marriott cancun? if so great choice we stayed there in dec.2008 as far as a safty factor, the water is safe to drink at the jw,also anywhere in the hotel zone.it is safe to take the bus up and dowd the coast along with taxi rides.
enjoy there is nothing to worry about.
Just finished a week at the JW. We enjoyed the property and the CasaMagna next door. Both are great properties. It seemed a bit windy at the JW. Not sure why. Next door was calmer. Lunch at the Beachwalk restaurant next to the pool at the JW was fun. Great view and fast service. We road the city bus into town almost every evening. 7.5 peso per person per ride. That's $1.05 compared to the $10 taxi. It was safe and entertaining. Took our college daughter and friend bar hopping for spring break. Aye Carumba! Carlos and Charlies was our favorite. Worked for students and parents. You'll see the police in black swat suit attire with wepons riding in the back of pickup trucks, More a show of force and presence than anything. We saw no problems, but then we got back to the JW by midnight to the displeasure of our daughter. Have fun.