Be honest and open with them ... If you want them to treat you like adults. We have no idea why they disapprove of you two dating.
Me and my friend really like each other. We are both 20 years old and have went on a few private dates. her parents a very strict about her dating or talking to guys. So we need away to tell them about us!
Have a family get together with your parents as well and as others have stated tell the plain simple truth. We are dating.
Both Single?
What country do you live in?
I'm guessing it's not in the Americas or Europe ... As at that age, you are legally an adult and can date whomever you want. (Well, unless you are still living in your parent's house)
just tell your parents simple
Make sure you invite them to the Wedding.
Did you mean "I and my friend"?
She's 20 why can't she date?
You're both 20 years old and there's no reason this girl can't date. Unless her parents have some reason to object to her dating you then you need to tell them instead of sneaking around. Her parents not wanting her to speak to boys is totally unreasonable, she needs a social life that includes boys.
As a parent I can understand their concern but as someone who had parents who never wanted me to date I would encourage your girlfriend to tell her parents, it's time she pointed out to them that she's not them, because they made mistakes does not mean she will. If she's firm, respectful and refuses to be drawn into an argument and tells them they have to trust her then she'll demonstrate her maturity.
At 20 years old she has to grow up, there will be other times in her life she wants to do things her parents don't necessarily approve of. Avoiding confrontation and not telling them will only cause more problems.