Kelly,
Yes, those SLF nymphs are a real nuisance! You don't say how high your balcony is, but you could blow them off with blower, or use a hand or shop vac. If you don't have one, sweep them off and put them into a bucket of soapy water or rubbing alcohol.  As for keeping them off, that's pretty much impossible.  They don't actually fly, they jump. Nothing repels them.  

Our page on Spotted Lanternfly Management offers several options for what you can do. The use of any insecticide on them is discouraged, as it may harm beneficial insects and spiders that are useful for controlling the lanternfly population naturally. Spiders, mantids, assassin bugs, and birds are some of their main predators.
 
Thanks for contacting Ask Extension.  Good luck!