The following dates are the best time to plant your veggies.  Remember that these dates are guidelines and to watch the weather for late cold snaps.  If possible it is good to plant just before a rain.  Planting later than these dates is alright if you are running behind on things.  You will just have a later crop.

Tomatoes and Cucumbers -- April 15 - 25
Peppers, Watermelons, Cantaloupe, Squash and Okra -- April 20 - May 1