I would dress like a bum and I used to joke that the car was my coat and tie...

There could be a bomb or a gang of jerks dressed in black making a youtube video down that way. 

It's not fancy but it's freehttps://www.biggerpockets.com/files/user/RichardF20/file/j-scotts-sow

I like the idea of moving the water and gas lines.Alternatively, is there a way of dressing up the entrance hallway so it feels like a mud room / foyer?

I am simply wondering what is common etiquette and dress at most meetups such as these?

In california the cost of the garage will be too much to see a return, and if the majority of the homes on the block have carports. i wouldn't get fancy with a garage, its just not necessary. 

Here is a picture of me beside a Cessna we chartered (admittedly, my friend decided to dress casual).

From the above article, it appears current plans are to close the Regal Downtown within just a couple of weeks for the new owner to begin demolition, and reopen the fancy new digs in about a year. 

When meeting with them always make sure you are dressed professionally and act mature.

It's sandwiched between the small downtown, the fancy gated community with a golf course, a large undeveloped tract of land and the river.