Crickets will chew on practically anything whenever they get the chance to, including other insects like mealworms, your lizard if it is asleep or is very young and unable to get away from the crickets in time, and even themselves. They are omnivores, meaning they will eat both plant and animal matter. They are also cannibalistic, so if you don't give them food right away, they will start eating each other. Alive. This might sound grotesque but I have had crickets running around in a plastic Kritter Keeper with half of their abdomen chewed off.
So yes, they will eat mealworms when given the chance. You can use mealworms if you want to, just don't plan of feeding those mealworms that are still alive to your lizard because it will have either died by then or will not be moving enough for the lizard to notice it. Or if you don't have anything at all to feed your crickets, you can always leave them alone to eat each other. The ones that are still fully intact will still be healthy because they will have been eating lots of animal protein. However, I think it would be better for you to offer your crickets other foods, including a mix of both animal and plant matter so that your crickets will have all that added nutrition from the vegetables as well as the extra protein and fat by the time you give them to your lizards.
