Yep! Melons especially love the plastic as it heats up the ground and you can get them going/growing earlier in the season.

I've never done cucumbers on top of plastic (I've used landscaping fabric instead), but it should work fine too.

Another benefit besides the weed blocking and the heat is that the plastic helps conserve water.

I grow mine on black woven polypropylene weed barrier fabric. So it is water permeable but keeps down the weeds. To get the melons up I cut a small hole in the fabric and cover it all with clear poly. The melons come up in 4-7 days even in March. I've been harvesting 25-40 lb melons for three weeks and will have them until October without fighting weeds.

Black poly will work as well but put it down early. Like I say I plant right thru mine. You will need provision to let water thru or for irrigation.

fruitnut, your season is ahead of mine. I have harvested 3 cantaloupes and have some Burpee Crenshaws ripening [my favorite when large and healthy vined to harvest]. My largest watermelons are only approaching 20 pounds now. I've got some Raspas, Sweet Princess, Sangria, Carmen, Gold Strike, Mountain Hoosier, Oranglo, and Cooperstown [seedless].

Wayne:

I've got the seeded Star Brite, Long Crimson, and Peddler. Seedless include Sweet Slice, Orange Crisp, Cut Master ESL, Trillion, Super Seedless 7167, Crispy Red, SX7405, Cooperstown, and Pasha Red.

Once again Star Brite is the clear leader. It way outgrew all the others and is the only one ripening fruit at this point. Harvested one today at 42 lbs and have a bigger one coming soon. Brix has been very good at about 13.5-14. I'll post pictures and a brix reading on the biggest one when it ripens. They are actually bordering on too sweet this year. And SB has good texture plus not too seedy.

Not sure why I keep planting anything else when Star Brite works so well for me. I've gotten the water and fertilizer just right this year for high yields and great quality.

You gotta go with what works for you. When I tried Star Brite, they were good growers, but I didn't like them.

For me, when Raspa is healthy and 25 pounds or larger, they are hard to beat. I have been eating watermelons for 70 years and know a good melon!