You give your plants a big advantage starting them inside IF YOU HAVE A GROWROOM SET UP. Ideally they should be about a foot tall when you "harden them off" (get them ready for outside by taking them out for 1 hour 1 day, 2 hours the next, etc., until they are acclimated to their new environment.
To find out the best time for planting in your area, call a local nursery and ask them when the last danger of frost usually is; plan to plant outside then.