Parking garage...that's an interesting idea. I've never tried that. I think people would still be upset if I did that - and not just the ones in my building, but the surrounding ones as well (open air parking lot). Not only that, but now they have a face to the tormentor (especially when I'm working on my range).
I do have the silent brass system - that's actually what got me into playing. I didn't know anything about mutes, and when I realized I could practice at home with a mute, I bought a horn again and dived right in.
Yes, a practice mute is not ideal, but it's better than nothing. On weekends, I try to play as much as possible during the day - not during "quiet hours".
I've been trying to come up with ideas where I can go to practice. My friend who also plays works in a warehouse area, and has invited me to play their once, but I don't want to practice on someone's schedule - especially when I want to practice as much as possible.
My horn: Yamaha 642II Neo. My mouthpieces: Yamaha 51D, Yamaha 53SH, Denis Wick SM4X Ultra, Doug Elliot 104 J8