additional fish would not be ok for the tank, this was said in another thread. The reason I say this is because of your intention on keeping the fish after the cycle has completed. The best bet is to get them goldfish out of the 5 gallon pronto...therefore in this case, your only choice is to go fishy. Here's a thread you can read on cycling:
http://www.aquariacentral.com/forums/showthread.php?t=81388
I know there is not room for another but what would I do with the fish I cycled with?
I think I am missing the point of cycling. If I am adding fish to spike the diffrent levals then waiting till it comes down to 0. Whats the point of doing it in the first place if it is allready at 0.