TanyaL, Texas gardeners generally have their "first garden" finished by the middle of summer. We plant much earlier than most. Many years we will plant our second round of herbs and cold season plants in late August or early September. It might be slightly different in your region (Texas is a really large state). Many of us have told you what we will do differently. We will MULCH and MULCH some more because we want to prevent water evaporation and cool the soil around plant roots. There isn't a perfect answer to this question. If you have a water well, be cautious, because wells in our area ran dry before the middle of June. The aquifer is not recharging and water table is dropping. The Llano River, all the LCRA lakes, etc. are severely below level and those are the main water source.
You could start your cold crop seeds, or at least some of them, inside and transplant to speed the growing season. You should see great results on most herbs by the end of March or early April. I hope you get a bumper crop of everything. Gardening can be great fun and really rewarding when you have enough to give to everyone and their dog. :-)