is this a solid fence or a wire/chain link fence? if its solid which side of the fence will you planting on? (n/s/e/w)
If you have access to composted horse manure I would put a few inches down after you weed anywhere you want to plant corn, peas, and cukes. follow that with a thick bed of hay,straw or yard waste. this ought to give you a nice grwoing medium to start with by spring. my personal
experience is that the beans dont' want quite as rich a soil. try to purchase bean seeds that have been inoculated.
anything that is climbing will do best if you plant within a few inches of the fence so that it can get ahold of it quickly. unless it is on the north side of a solid fence where it wouldn't get sun quickly.
unless your soil is really poor, rocky or waterlogged you don't absolutely need to make the bed raised. your climate, financial and work commitment dictates how high you can make it. if you live where it is going to get really dry for a while during the growing season, a deep bed makes it harder to keep watered whcih can be a serious issue for shallow rooted plants such as peas beans and cukes. a raised be will be more subject to temp fluctuations which can work for you or against you. (heat up faster in the spring, but cool down faster in the winter) so it depends on your climate.