Germination isn't the problem with the spring things. Even things that grow in cold usually will germinate well at higher temps. The issue is that they will bolt in warm weather. They grow best when it's cooler. If you have a shady spot and if you can keep night temps relatively low, you might be fine. I'm in zone 5, but I'm on a roof deck and it's hot as blazes; if I planted these things at this time of year, I would be wasting my time. You might be able to go to a store and find some lettuce starts. You probably have 6 weeks before it gets really hot and the lettuce would bolt. If you got in partially grown plants, you could use the "cut and come" method" with leaf lettuce or even romaine - just cut off some outer leaves, leaving some core to the lettuce. Those inner leaves will continue to grow and in a few days or so you can cut a few more. Next year consider getting these things in a bit earlier, such as late March or early April.

Katie, My last batch of my sweetpea plantings for a late winter harvest are just flowering this week and I felt I was pushing the season when I planted them. Lou

Check with your state's Extension Service. Each county should have it's own Cooperative Extension Office which provides free publications and information for the asking. They will have valuable vegetable/gardening tables available specifically for your area determined by universities, and horticultural research scientists who have collected data from growing those crops in your state. Your tax dollars are already paying for this service so you may as well get some use out of it. See how detailed these examples are: Vegetable Planting and Planning Calendar for Missouri (download the pdf) complete with spring and fall planting dates (underneath the spring planting dates for appropriate crops), how much to plant per person, etc. They can also tell you the average last frost date for your area and ideal planting times for specific crops and varieties in your area. Here is an excerpt:

I planted them all spring and summer last year with great results in pots. They grew vigorously then petered out so you want to stagger the planting to get continuous harvest. They grew to be over 5 ft tall above the pot, and planting quite a few in a 2 1/2 ft tall by 1 1/2 ft wide pot didn't seem to bother them. Planted them in a circle around the outside of the pot about 5 inches apart and then in the middle with the same 5 inch distance from all the others. I had to duct tape 5 ft tomato stakes together to make them long enough to support the tall growth of the plants. I used velcro tape (greatest invention in gardening history imo) to support them. I planted into late summer and harvested into November. I didn't notice that they cared when they were planted in terms of heat and didn't care about the cold until it was really cold. Good luck!