How is it you only found out about the under 20 lb rule after you bought the condo?
We are trying to buy a house in Florida and they have similar HOA restrictions there. We have a lot of pets - 3 dogs under 20 lbs, 3 birds. We had to pass on tons of houses due to HOA rules, because I am not willing to give up any of these animals to move.
Really tough to find a non-HOA in FL but we finally did.
It can be a long drawn out and, in the end, fruitless battle trying to change HOA rules.
Wiz - the weight restriction is the way they try to keep potential hazzards to a minimum. They used to do it by breed, but maybe it was too easy to get around that. In Ohio, there are still vicious dog laws but in other states they just ban all larger dogs.