First, if you are having trouble with low blood pressure, talk to your doctor about it. I'm not aware of caffeine having any real effect on blood pressure.
Second, caffeine is a stimulant. It probably helps performance and is generally harmless in moderate amounts. It's also useful for getting your bowels moving, so don't drink stuff with caffeine so close to a race you might have to make a pit stop. The NCAA limit is the equivalent of something like 10 cups of coffee in an hour, which would probably make you sick and jittery and degrade performance anyway, so just don't go nuts with it.
Just try drinking a cup of coffee 1.5 to 2 hours before a practice run and see if it helps. Don't experiment before a race.