You should be able to. New Virgin phones aren't locked to Virgin.
The way you can tell is if the logo isn't printed on the handset and you don't see a swirly Virgin Mobile "infinity" logo when the phone is turned on.
Just make sure you have removed the Virgin "Mobile Rescue" Security App (if installed) before you swap SIMs. If you do need to uninstall it, make a not of the PIN first in case you want to put the Virgin SIM back in.