Wait until danger of frost is over. That will allow the soil to warm up, also. Your friend is right in that these herbs are perennial, but they are also young and have led a protected life.
When they hit the ground, remember not to fertilize since that leads to lush foliage and less taste. Also harvest frequently, since that keeps the herbs producing new leaves and they don't get leggy. You may want to keep your mints in pots since they are invasive. A buried bottomless pot with about 2" of rim sticking up out of the ground will keep a mint somewhat in bounds (and you can see the creepers sneaking over the rim and cut them off!).
No thyme? You must get some thyme!

If they have been sheltered in a greenhouse, your plants will need to be hardened off. If you omit this crucial step, your plants may survive in spite of it but results will be so much better if you take the time to harden off. Check the link below for all manner of reading material on the topic.

And marlin is right. Wait until the danger of frost is over. Get your last frost date from here frost dates. My guess is you'll have to wait until mid to late May based upon what you say your zone is.

FataMorgana

Here is a link that might be useful: Google - hardening off

WOW! Great info, thanks do much... i will go check the link on "hardening off", oh, and i do have thyme! Thats the one thing that made it last year, English thyme and it looks great:) also i do have one lemon thyme plant in the new group... i do love it:) Thanks again and all the best with your own gardening this year:)

One other question, since it will be a month til i can safely give these guys a home outside, i have them sitting under a 15w flourescent energy saver type bulb cause it's overcast often in the spring and i move them between there and the window when theres sun coming thru... will this work for a month? The oregano is already getting kinda leggy, i dont have a lot of money to spend, but since i already invested in the plants i would hate for them not to make it~ will they need more light?? Yikes! And are they too young to start pinching them out here and there or would that improve their strength? Thanks so much, your input is invaluable:)

Pinching is one way how the greenhouses get them so full and lush. So as long as you don't take too much off you should be fine.

However for you and others who have plants to harden off, put the plants in shade first then gradually bring into direct sun. The leaves and stems are subject to sunburn if they have been grown inside or in most nurseries. Later in the season most nursery plants will have received some sun but if you purchase from a greenhouse or nursery and the plants have a cover/net above them they still need several days to become accustom to direct sun.

great, Thank you! i will begin pinching, but delicately:)
Best regards~