1) Don't worry about what other people on the bus think. Most will assume it's for your kid or your nephew or something like that. Some will be utterly green with envy. :)
2) Lots of adults play with LEGOs. There are even instructables about how to keep your LEGOs tidy and easy to find.
3) Don't worry about where you'll keep it. Eventually you can take it apart, and put it all away. Then you can build it all over again in a few months!! Or, better yet, build other things from it's pieces and let your creativity wander.
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