lilyluv,
I would not spray them just yet -but- keep a really, really close eye on them and when you first see any insect activity spray. I would not use a heavy duty spray at first because a good jet of water can dislodge many insects. You can use a soap spray now if you absolutely must spray. (Safer brand is what I use). It is easier to prevent large population of bugs if you inspect your plants daily. Be sure to look under the leaves closely. I spray in the late evening to prevent killing the bees.

DL

I wouldn't use a bug spray until you see bugs, then use something specific for the bugs you see. It's not usually a good idea to use insecticides as a prevention. You're more likely to kill the good bugs, like bees and lady bugs, and you could poison yourself or your family.

I've grown most of the same vegetables you're growing in containers for many years and most of the time I haven't needed to use insecticides at all. The exceptions are cabbage family plants, which often get cabbage loopers, and cucumber family plants (cucumbers, melons, squash), which sometimes get cucumber beetles or squash bugs. I use Dipel or thuricide, which are safe biological controls for cabbage loopers and their relatives. I also have used Neem oil and spinosad, which are safe organic insecticides that kill a wide range of bugs including all the ones I've mentioned. Neem oil can also be used as a preventive to protect your tomatoes from diseases. In my experience, tomato diseases are the only thing I've had that actually killed anything in my garden.

You could always go with Ladybugs but if you haven't seen any insects on your plants yet they might not have food so they won't stick around.

I've had great success with all the options Ohiofem suggests, Neem, spinosad, and Bacillus thurengiensis (BTK, Bt worm killer, thuricide). Like the others said, its best to inspect your plants everyday (it doesn't have to take long), not only for your safety, environmental responsibility and the health of your plants, but because most insecticides are essentially useless as preventatives. Antifeedants and insect growth regulators are exceptions, so you can look into that if you have the inclination. If you want a broad, but safe preventative, neem is your best bet. To use it effectively, you have to spray much more regularly than a conventional insecticide, so be honest with yourself about how much time/effort you're willing to invest. More dilute + more often doesn't always hold, but IMHO it does with neem - it minimizes plant toxicity, and maintains effectiveness.

Squash borers can be heartbreaking - they totally wiped out one of my zucchini plantings this year. Unlike other pests, once you really notice the problem, the damage is done - there's usually not much you can do, especially in containers. Personally, I would start using a weak insecticidal soap on your cantaloupe and summer squash stems as soon as you see the first flowers, twice a week. Be very thorough about spraying down the stems, particularly at the base of the plant and about 8-10 inches up the stems. Read up on them for more information.

Spray very late in the evening to protect bees and to reduce the stress/phytoxicity for the plant. Never spray when the plants are water stressed.

Greentiger's comments about neem oil reminded me of an old post from Al (tapla) I read a long time ago. He actually uses it as a preventive. So I may have to rethink what I said. Check out the link below if you're interested.

Here is a link that might be useful: Al on Neem oil

Thanks so much for all the responses! I have been checking every day, but no bugs yet. Think I might try the Neem as a preventative, just in case I miss something. The plants are all getting so big, I think I might have planted too many plants per container. I will know better next year. It is so nice to have them up where the bunnies can't reach them, and easier for me to reach them! Thanks again!