• neighborhood watch
• neighborhood kids
• It's a beautiful day in the neighborhood. (Mr. Rogers)
• neighborhood block party
• It's in the neighborhood.

A Garden that is in a neighborhood.

He is the neighborhood.

Neighborhood is a noun.

No, the noun 'neighborhood' is not a standard collective noun, however, any noun that suits the circumstances can function as a collective noun; for example a neighborhood of artists, a neighborhood of shops, a neighborhood of immigrants, etc.