I start them in 1gal pots around April or May and then plant around June. I did use the grow tent indoors to start them but you can get them going once it is warm. If it is warm during the day and cold at night you can move them in and out each day.
I have more starters going now that I germinated in my garage 2 weeks ago and moved to full sun right away when they sprouted. Those are going fine, they can straight into full hot sun as sprouts.
Dimitry, you came to my house on the hill out in Poway not that long ago. Remember? I planted 18 water melons in my front yard and 18 tomato plants. The deer decided they like tomato but left the watermelons alone.