Using Minoxidil once daily will still be extremely beneficial at treating hair loss, almost just as good as twice daily usage. I myself use Minoxidil twice daily to get the most out of the medication, but yes, you can use the treatment once daily and be good to go.
I've always used once a day (mainly for the inconvenience factor). It has caused slight regrowth and stopped hair shedding for me. 2x a day will probably give you better results.