Not a ton to add, but a few things on how to keep expenses low at the start so you can splurge later.
1) Buy fruit at mercado central and each fruit for lunch or dinner once every other day or so.
2) Eat at Mercado central- 3 bucks a meal no problem.
3) Walk during the day, or take the bus around. Its really not that bad. Split cabs at night.
4) Booze- Often a big expense. Buy a couple of bottles at duty free. Have a flask with you.
5) If you are multi pop a day guy, try some of the lower end MPs around calle 6 and start the day with a half hour session.
6) On low budget trips I have had in the past, I like to be conservative at first, so I can party hard at selected times.
7) Carefully back things you will need so you don't have to buy them. Ibuprophen, condoms, sunblock, ect.

Watch the little things, they add up fast.
9) Since you are going for two weeks, have a couple of days when you only do a couple of half hour sessions at MPs, or one, god forbid. This alows you to keep the money for when you want some TLNs with some hoties.
10) Try a day or two of non pay for pu*sy, and try to pick up some ladies out of the gultch. The nice things is, if you stike out, you know you are getting laid whenever you wish.
11) Try some low end night time places like Bar Camelot (is that even around???) or Molino Rojo.
12) Forgot to add this, but buy bottled water at the story in large jugs. Have one water bottle to carry around. Buying random drinks adds up a lot.
Mix and match some of these statagies and you can save a bunch a day and not feel deprived. I personally LOVE eating a meal a day at the Mercado central or an inexpensive soda, and feel better when I eat one light meal a day (fruit). Make sure to plurge big time on the chicas and a good meal from time to time. Enjoy.