I was looking up some bikes for you and I found a couple of good deal for a good starter bike. This will be good enough for your first couple of triathlons until you get a little more serious. Some of these bikes will be too big for you as you are under 5'3. There are plenty of deals out there, this is just from things that were posted on
Craigslist. Most of these bikes are not going to fit you but I wanted you to see what kind of deals there are to be found. This is only two days worth of Craigslist and there are other sites that you can search on. Just as an fyi at 5'2 you will probably need a bike with 36"-42" frame, somewhere in that ballpark.
One of the best deals that I have found. This bike is $675 probably is worth at least twice that including all the gear that it comes with:
The tire repair pack, Look pedals, Digital speedometer, Diadora shoes and cleats, matching Le tour de france water bottles, helmet, gloves and sunglasses will be included if you want to take them.
Pros: Good starter to Advanced bike. No upgrading or spare parts needed.
Cons: Mildly expensive, if you are not
sure you are going to keep racing

Like new, rarely used Raleigh. This is a 700 dollar bike for 350 pretty good steal for a bike that has been slightly used.
Pros: Great Deal.
Cons: Will need some updating cost in the future, even though it is race ready
I know this one is a little out of your prices range at $4500 but I feel in love with bike when I found it. I figure I'd put something here for you to dream about.
Pros: Very fast bike, with Easton tubular tires
Cons: No aero bars, alot of lunch money

My bike !! At a $110 this bike is a steal for a first time racer. Will need to update your ride as it will keep you competitive, just not very competitive.
Pros: Cheap Price, Comes with a helmet.
Cons: Will need updating...
This bike is like new, was purchased at 1400+ taxes plus Look KEO Easy pedals retail 79.99. He is asking 1100 obo.
Pros: Fairly good deal and great looking bike
Cons: Mildy expensive for a starter bike

Cheapest starter bike that I found ask $59. Look at all the pink !! For small to medium women, which you will be able to fit on. Looks like a mountain bike that has been turned into a road bike.
Pros: Very cheap, PINK
Cons: Only a starter bike if you get serious you need a new one, PINK

Blackwheel 100m Carbon Wheel for 470. These are very fast tires with only 20 miles on them. You could always get a cheap biker that can be easily upgraded, by added cheap parts as this one.
Pros: Blazing speed
Cons: Will not fit on every bike, not cheap
This is a bike that I posted up for my friend Amanda who rides a Bianchi in Celeste as well. At 850 this bike is a decent deal.
Pros: I already told you its a Bianchi
Cons: No aero bars.
Clicking on any of these pictures will bring you right to the post on Craigslist if you wish to read more information about them. All of these bikes are in the South Florida area and there are about 40-70 new posts for sale everyday. Hope that shed some light on your questions. Leave me a comment if you have questions about anything else.