Buy this instead: http://dallas.craigslist.org/dal/bik/3291900164.html
Seconded the 26" mountain bike.
Other reasons to go with a mountain bike:
- They will come with flat bars, which you will need for polo. One less thing to replace.
- They will accommodate the fattest tires you desire - swap them out for some durable 26" commuter slicks.
- They will have canti/V-brake mounts, which you will want for polo. Road calipers - especially old, vintage road calipers - simply do not have enough stopping power for any level of polo beyond "First Month Beginner".
Basically, if you get that old road bike, you won't have as much fun at the start, and if you do you'll have to invest a couple hundred bucks in new brakes, new bars, new calipers, and a bunch of other things before you can get to the "next level". And then you'll still be playing on a shitty old road bike frame, with kinda upgraded components.
If you get the mountain bike, you'll be able to play and ride fast and stop and have fun right from the start, with no extra money invested.
Either way, if you're still playing in a year, you'll probably be building a purpose-built polo bike (and spending the dollars that go with that). With that in mind, there is no reason to start with a fixer-upper that you're going to have to pour money into and it still won't be good. Start with the ready-to-go 26" mountain bike.
Frame and forks looks too weak for bike polo. If you are looking for something cheap and solid, with big tires, you should look for 26' wheel moutain bike.