Hi John
I had great success with Melons last year and will def be doing them again, I have 3 greenhouses, 2 are positioned in full sun and one is under the trees so it gets early year sunshine (when we have some) and is cooler during the hotest months. The melons were grown in one of the full sun houses along with cucumbers and the tomato were grown in the other one with peppers and interplanted with lettuces. The greenhouse under the trees I use to raise all the seedlings before potting them on, then I use it to raise fast batches of salad leaves etc. I also accidently planted some melons outside with other squash plants and they did well too, maybe it was just a good year for them!! Tomato and cucumbers like different levels of humidity so bear that in mind when you are planning, I know some people that have sectioned off the greenhouse with a sheet of plastic in the middle to get the different humidity levels they need.