We usually tip the maid service $2 a day and the restaurant waiters around $3 or so every time we go eat. We also always tip at least $1 for each round. My wife and sometimes takes turns, depending on who's quicker to get the money out. The waiters at Patty O's seemed to really appreciate it as we've had to ask them to put less alcohol in our rum and cokes, as they were too strong. Also, I distinctly remember where there was a line of people waiting to get drinks and one of the waiters saw me get up off my chair to make my way to the bar and by the time I arrived, he already had us another round of drinks made for us. The level of service we've received at Temptation far surpassed the service we received at Sandals in the Bahamas, where there was absolutely no tipping.
In my experience, the front desk staff will only break larger Peso notes down to 50's and not 20's and I'm generally too lazy to leave the resort to seek out smaller change, so I always bring a big stack of US$1 bills down with me so it's easier to tip everyone frequently.
Now that I have been a whopping one time I have learned that I will bring very little USD with me. I will bring enough for USA Transfers and the Boobs Cruise. The rest I will bring in the form of Pesos 20's & 50's.
