What's the best spot in the garden to plant tomatos and cucumbers? I find you can train the cucumbers to grow on a trellis, but I keep having a problem with the tomato plants overshadowing the smaller plants and taking all their "sun time". Also, does it matter if they're on the east or west side of my garden?
Yes, cucumbers can be trained to grow upright on a trellis.
Placement of tall plants such as tomatoes ideally would be at the north edge of the garden so they would not shade other plants. Otherwise, it makes little difference whether they would be on the east or west side of the garden. If placed on the west edge of the garden, they could shade things such as lettuce and spinach that don't like heat, and thereby slightly extend the productive season for these somewhat shade tolerant crops.