Should I buy a new bike or get old Schwinn repaired?

[raerae21]

I found a Schwinn Le Tour III at a thrift shop for $4.00. It was selling for $8 but believe it or not, it was half off bike day! So the wheels are straight, I got new tubes and tires but the back one keeps going flat and I have put a new tube on it multiple times. The frame seems fine i guess (I don't know anything about bikes). The chain was rusty but loosened up after I greased it and rode it a lil. The brakes work but I have to squeeze semi hard. The gears just do what they want but they do shift and maybe thats because I don't know how to work them. I just want to stroll around my hood and to my college which is just a few blocks away...so should i get it repaired or give up on it... I am not a serious rider at all but I would like to go ride in the afternoons or something..so any advice..