http://www.buglogical.com << this is where I order ladybugs from. We do get some ladybugs outside, but I order them and let them go inside the house when I see the first signs of aphids on my overwinters.
Another thing to watch for, inside or out, is mites. I have had no problems with mites outdoors, but found broad mite damage on the tomatillos I started a few years ago inside. Unlike aphids, broad mites are too small to see with the naked eye - you will see their damage before you see them, unless you regularly inspect your plants with the use of a jeweler's loupe. Again, my answer is beneficial insects.