That advice (never leaving your instrument in your car) was going to be my answer to the "some people would find it obnoxious" to bring in your instrument remark. I frequently bring my guitar into people's homes and good restaurants where I have no expectation of playing. I simply state that, as a "professional" musician (no snickering!) I never leave my instrument in my car. I ask them for a corner (preferably where I can see it) to store it in. I have never had any complaints from my hosts about my bringing it inside and on a couple of occasions I have been asked by my hosts to bring it out. There are lots of once-upon-a-time players out there whose eyes light up at the sight of a good instrument. I even had the chef at one of my favourite restaurants come out and ask if he could first see and then play my guitar. You never know.