If you want to make the election and attach it to your tax return, you will have to file your federal return by mail. TurboTax does not support attachments in e-filed returns.
Once made, this election cannot be withdrawn without express permission of the Commissioner, IRS. This means that if you sell the rental property, you won't be able to claim the mortgage interest as a Schedule A deduction.
The following blog discusses this issue in some detail: http://www.taxprotalk.com/forums/viewtopic.php?f=8&t=3061
