.. well I say go for it! I have no knowledge in the area of sperm donors, but you shouldnt have to have a partner in order to have children!
I'd imagine people would tell you that you have plenty of time still, but you know.. what if you dont and your body wont allow it after 30?
So in my opinion.. I say do what you want, as long as you dont think you will regret it. Goodluck