Now that special needs training is more common, such a setting may actually be available to you at a reasonable cost. Another way to make a typical preschool work for your child is to tap into local autism agencies to provide a one-on-one aide and/or itinerant therapists to work with your child in his preschool setting.
That said, however, typical preschools are rarely prepared to offer a child with autism the support and therapy she needs to progress rapidly. What's more, children with autism can quickly run up against their own and others' limitations.
For very young children on the autism spectrum, social settings may be extremely challenging. Children with autism rarely learn through imitation (one of the basic difficulties inherent in autism), so just being around typical peers usually isn't a great way for them to learn social skills. And the noise, physical interaction and high level of expectation in a typical preschool may be overwhelming.
Even with a one-on-one support at school, an autistic youngster may have a terribly difficult time with behavioral and/or sensory challenges, such as circle time, sharing, and so forth. Teachers without specific training may have no clue how to help your child manage his or her behaviors, and they may perceive their behaviors as "bad." To manage the situation, you -- the caregiver -- may need to provide ideas, be flexible about attendance, or even show up to help out.
Meanwhile, ordinary preschools are not set up to provide the kind of intensive therapeutic programs so often recommended by early intervention experts. As a result, programs like Applied Behavioral Analysis (ABA) cannot be implemented at the preschool, meaning your child may wind up with a double schedule of preschool plus home therapy. This may be fine, or may be just too much for your child to handle.
The bottom line: If you are determined to try a typical preschool for your child with autism, choose the school carefully. Limit the hours your child will be at preschool. If possible, set up a one-on-one aide to support your child. Keep your expectations limited. And be flexible -- if it doesn't work out, have a "plan B" ready to go.