Cucumbers are heavy feeding sprawling plants. I plant two per 3 X4 foot section of raised bed. One such section contains a day lily or two and they co-exist quite nicely. To maximize the space however, I generally would plant an early season crop like sweet peas, arugula, lettuce, spinach. By the time you plant the cucumbers, the early crops will be nearing the end of production. I just nestle the cucumber starts or seeds if direct seeded, in between the early crop plants. When the cucumbers get enough size to start crowding the bed, the early crop will be finished.
Eclectic gardening style, drawing from 45 years of interest and experience. Mostly plant in raised beds and containers primarily using intensive gardening techniques.