I’m active duty military, and routinely have to travel away from bike/trainer, etc. I am also a triathlete, so during those times I focus on running, or if there’s a pool available I’ll swim. I like to use spin bikes as a substitute, and there are some out there that have “power meters”, while they’re not accurate, at least I can get a pretty good RPE workout in. Most gyms will let me use their bikes when they’re not actively in class. Otherwise, I’ve gone the route of sitting for an hour or two on a Lifecycle fitness bike and it does the job, especially for “base” training. In other words, I can sit on the bike, get my HR into the 140s and keep it there with a 95rpm cadence and get the gist of the training.
All of that is sub-optimal, but sometimes you gotta do what you gotta do. Ultimately, it’s about preserving fitness as best you can when you’re not able to train ideally. I spent around 75 days without access to my bikes or a pool during this year’s base phase. My “A” 70.3 race was roughly 3 months after that period. I established a solid base of running early, supplemented with cycling until the “off period” then used the spin bikes and exercise bikes as mapped out above in addition to a treadmill. While I definitely would’ve been faster in my “A” race under ideal circumstances, I was still able to meet my split goals under those less than ideal circumstances and have a really good race.
Mentally, I had to accept that I was making some sacrifices in training because of my job, and make sure that I was OK with training as well as I could under the circumstances, not worrying about the fact that it wasn’t the optimal training. In other words, do the best you can.
I personally wouldn’t ship a bike and trainer for 30 days, but that’s me.
Edit: missed that you’re returning to your state CX race. Yes, in that case and on that timeline, I’d probably ship a bike and maybe even a trainer. This past year, I had time to build prior to my event.