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?
It depends on which Buddhist tradition that particular temple belongs to.

To avoid rampant anti-Japanese racism in America stemming from the 1940s, when Japanese Americans were placed in internment camps, Japanese Buddhist branches like Jodo Shu and Jodo Shinshu conformed themselves to a more western model of creating religious spaces when they settled in America. This is why the American branch of Jodo Shinshu is called "Buddhist Churches of America". They often have pews, a minister speaking from the pulpit, youth groups, etc.

Temples from other traditions usually don't model their space after western religious models. The sangha's "mode of operation" depends on the tradition, which school of thought that sangha follows within it's own tradition, and of course, the Buddhists themselves. So when visiting, these sanghas should be understood on their own terms as much as possible, leaving expectations at the door.