I also use a hardshell case. I ship my bike ahead of time to a shop and have them put it together and then again at the end of the trip I have a shop break it down and ship it home. I have used both Shipbikes and Bikeflights to generate the paperwork (they both use FedEx for the actual shipping) and their prices are a fraction of walking up to their store front and shipping it. I have always been able to get the shop at the beginning or the end of the trip to hang on to the box. First step in getting to "yes" is to ask. I also give them some money for their trouble.
On a similar thread a few months ago someone else mentioned they've gotten their hotel to help them out on this problem. If you like to do your own wrenching this could be best as it also avoids coordinating when you're passing thru with the bike shop's hours.
There is a middle ground here between the hard shell case and the used bike store cardboard box. Both these shipping places sell reinforced cardboard boxes that look pretty sturdy. While I'm sure they aren't as tough as your hardshell they would make the logistics a whole lot easier. They're sold for around $40 and you can either break it down and use it again or toss it, but it should give some additional level of protection.
I'll also mention that I was hit with a $170 customs fee when I shipped my bike to Canada last year. I don't know what the US customs policy is on bikes but you may want to check into that and be ready for it whether you take the bike with you or ship it.