Can an existing 3 year old C-corp switch to an S-corp?

I own a construction company in California currently a c-corp. I'm thinking of switching to a s-corp to avoid the "double taxation". I was just wondering if I can still elect to be taxed as an s-corp even after 3 years. I've read that that form 2553 has to mailed to the IRS within 2-1/2 months, I would appreciate any input, thanks.