This is explicitly a ban on "the substantial equivalent" of marriage, such as civil unions and domestic partnerships.
The backers of Amendment 2 are deliberately misleading the public by constantly calling it a ban on "same-sex marriage," and the media are reinforcing that misconception.
The wording of the proposed Amendment 2 here in Florida threatens the continuation of health insurance and other benefits provided by employers to many couples, straight or gay, young or old. In Michigan, which passed a similar constitutional amendment, the courts just decided that if you're not legally married, you can't be on your partner's medical plan, or have visiting rights at hospitals, or receive pension benefits.
"Gay marriage" will not be on the ballot in November -- rather, stripping away partnership benefits and health insurance for all unmarried Floridians will be decided.
This is how conservatives get majority votes -- they lie to the voters.