Yes, it's okay to leave them. You'd get a wide range of opinions over on the Soil, Mulch and Compost forum regarding shredding them first since they break down faster when shredded - not to mention being more "aesthetically pleasing" as a mulch and less likely to blow back where you don't want them.

But as a practical matter, and I've always been somewhat practical, you won't do any harm. I've got maple leaves by the ton and no way to shred them. Although I rake the lawn clean, whatever falls on the gardens stays there until I clean them up in the spring so they don't become a thick, wet, smothering mat. Then it's on to the compost pile or piled up in an out of the way area to become leaf mold.

It would be even better if you could till them in in the fall.

I always leave Oak leaves on my flower beds, since we have tons of them. They curl up and don't mat down like Maple leaves do, and water can still filter through to the soil. They eventually break down, but in the mean time they make a great mulch, as long as the flower bed isn't in a windy site, where they might all blow away.

I don't have a veggie bed, so can't give an opinion in that area, but Leftwood's advice above sounds great for a veggie bed.

Julie