It might stop the leak, but then again it might not. It will probably clog the lower portions of the (block's) water jacket, which will cause the engine to run hotter and may prevent you from using a block heater should you want/need one. Later (much later), it will flake and circulate through your cooling system, plugging passages.
I keep a single tube of AlumaSeal for emergency use only, and if I'm forced to use it I follow up with a proper repair just as soon as possible and an overkill cooling system flush which I repeat a few months later. It can make the repair more difficult by hiding the leak, and it will shorten the lifespan of the water pump.
You'd be much, much better off just taking a few hours to fix the problem before your trip. It might be a royal PITA but it'd make a lot more sense.