the live plants should be unaffected by the cycle period, unlike fish they can handle ammonia and nitrite. I have found them to speed up cycling a bit too. not the beginning part of building ammonia which converts into nitrite, but they have really sped up my turning nitite into nitrate and breaking down of nitrate. so I would recomend them, but as dragon said, be sure to add fertilizer for them. plants need food too. and some need mopre than that. CO2, great lighting etc. so be aware of the plants you buy.
hth
richard