I've never tried goo gone but twice now I've put what I thot was red colored glass in the dishwasher but it wasn't colored glass but some sort of colored coating over white/green glass. This coating turns cloudy in the DW and I've had to scrape it off. On this last one DH used paint remover which worked fairly well except for the crevasses. I really need to look closely at cheap YS colored glass before I buy it.

As long as they aren't kept in direct sunlight, I don't think it should be a problem in your zone. I've used the baggie method more often for tenting and the only times I've roasted ones due to heat was when I forgot about them somewhere where direct sunlight got on them for too long.

What an amazing project for elementary school kids. If they all started saving 2 liter bottles and took them to school to collect, by January they would have enough and then the greenhouse, reuse/recycle, planting lessons could begin. They could grow flowers to plant at the school, or even vegies. My MIL goes through one 2 liter per day (minimum). I bet it wouldn't take long to get enough to experiment with. So what if it only lasts a year or two. Just keep saving for replacements.

I found a few ideas HERE at Apartment Therapy. I've been saving hubby's wine bottles to use for watering plants since I'm terrible at remembering to do so on my own. I don't think you need the Plant Nannies like they show though. I've seen glass bottles used as too, I don't really care for the look. I think it would be fun to make garden lighting with them but I'd first swirl some stained glass looking paint on the inside in the colors of the drinks and then add lights.