What are proper expectations to have about a Sangha?

In my area, there are many Buddhists centers referring to themselves as centers, meditation centers, or monasteries. These all seem to be various expressions of a Buddhist Sangha. However, being in the Mid-West one tends to expect the Sangha to be modeled on or similar to a church or synagogue. What are the proper expectations to have about being part of a Sangha? Should Westerns expect a sangha to conform to the Western notion of religious institutions?