I take it they are getting as much sun as they can receive without getting burned.If you bought your begonias from California they may not bloom till next year;if you bought them from England (through White Flower Farm) they are mature enough to bloom this year.If you planted them directly in the pots as tubers you may have to wait awhile.If you started them indoors early and planted them in pots when groen they should be blooming.I have more than 20 in pots ,most of them from White Flower Farm,the rest from Antonneli's in California.So far only three have been blooming but there are buds on most of the others.You could use a bloom booster fertilizer(don't overdo)>Antonnelis has a special fertilizer to encourage and sustain blooming.Two years ago most of my the 26 begonias did not bloom;I gave them more sun and they bloomed their heads off.It depends on where you are and how long the growing season is.I'm in Northern Va.and the season goes (for begonias) tii the very start of October(but by then the su has gone down lower in the sky).Good luck and dont give up.