The availability of garden design courses seems to be closely aligned with regions :-)) The more urban areas of the east coast offer many, as do similar areas on the west coast. And there are quite a few good choices in the Great Lakes areas - Chicago, the twin cities, etc. My suggestion is to look for one in the area YOU wish to relocate to - regionality is always going to play a factor with regards to popular "styles", climate/weather conditions and plant selection.

There is a difference between a career as a garden designer and that of a landscape architect. Garden designers typically focus on residental projects while LA's are often invloved in a wide range of commercial and institutional projects as well as residential. There is a significant difference in training required between the two, so make your choice of career path before you start your education.

While some programs can be completed in a single year, I think you will find that most are two year programs, typically ending with an AA degree. These are often offered via community or technical colleges. These tend to be quite affordable and also flexible in their hours, so that those working a day job can take advantage of them. All are going to offer somewhat similar courses........enough to provide the basic skills. It is important to understand that "book learning" or a structured educational environment is only the beginning - hands-on experience is essential and that is usually only avaiable working in the field as a laborer or apprentice.