Does a Diablo 3 guest pass let you play with regular players?

Solution 1:

Per their official website:

• Act I up to the Skeleton King is available
• Level 13 cap
• Matchmaking available only with other Starter Edition players
• No Real Money Auction House access
• Global Play is not available. Players attempting to connect to Diablo III Starter Edition in a region other than their Battle.net Account's home region will receive Error 12. See the Global Play support article for more information.

"Starting Edition" player, meaning players using the guest pass. So you are limited to interacting with them only.

Solution 2:

Players using the guest pass are restricted to playing with other guest pass users. You can not play or trade between the normal game and the guest pass version