^ ... just try and avoid the travel agencies ... there's a reason they are in business ... and if you think they can/will get you a better deal, well, then you need to reconsider ... they make $$ by making your reservations ... and from my experience, I've always been able to show up somewhere for vacation and been able to get a better deal in person ...
... it does suck to know that you're going to a place where you don't know anyone and you can get ripped off if you're not careful - but for the most part, if they know you will walk out of their hotel and go to another one (don't look desperate), then they will give you a huge discount ... especially for cash transactions ...most will also give you great deals on lodging/meal packages ...
... unfortunately, I haven't been to Cancun for over 10yrs ... but I/we just showed up and found a place the day we arrived ... 4 of us ... got 2 adjoining rooms for around $125/ea per night and it included breakfast and dinner ... meals were buffet style ...
... gave a CC for a security deposit ... paid 1/2 upfront and then paid for the remainder of the stay 3-4 days later ... was there for 6 or 7 days/nights ...
... parasailing and diving were the most reasonable fun things to do ... just make a cash offer and don't budge ... then the next day ... offer a little lower and tell them that (if they agree to that price) that you'll be back the next day for more ... they love repeat customers ... and you may have to wait in line for the tourists paying top dollar for the same thing ... but 30 minutes later - you're in for less than half of what the other guy just paid...