Crop rotation in a small garden does not have a lot of benefit when it comes to insect or disease control. B/C in a small garden, the different families are not going to be far enough removed from where they were last year to do much good. Crop rotation is most useful in monoculture crop farming where acres of a particular crop are planted at a time. They are then followed by a different crop the following year.
The only real benefit to be had from crop rotation in a small garden is to help prevent depletion of certain nutrients from the soil, or to help build nutrients after a heavy feeder has been in a certain area. For example: Plant corn or potatoes (both heavy feeders) where you had peas or beans (nitrogen fixers) the previous year. Application of a good compost will help in that regard also.
There are some benefits to be had from companion planting, and intercropping. I've found that potatoes and corn make good bed mates. Most likely b/c both are heavy feeders, so I am heavy handed with the soil amendments where they are planted.