...and you currently look like a pop up and not a real business
Would the notion of a pop-restaurant put me off going in? No.
I have seen so many businesses splash out on image when there's actually no substance behind the facade but by all accounts this is a decent restaurant, which means that they've invested well in the things that matter most to them and to their paying customers. So what if they haven't got around to doing the sign yet? They pay the rent and rates on the premises so it's their prerogative to develop their business entirely at a pace that suits them. Whatever the reason for the lack of signage, I wish them well regardless.