It really depends. The biggest factors will probably be cultural. If everything is optimal and assuming the seeds were mature enough, I'd expect to see some green dots in as little as 4 weeks. Some may come up sooner but most will probably be one month minimum. Could take as much as 6-8 weeks, or even several months.
The Mexipedium could be tricky. Some terrestrials need darkness and/or cold stratification, and some are very picky about medium strength.