How do I get my A/C to blow out of the dash not the defrost vents.

It's got a vacuum leak!! Look under hood on passenger side for a 'small' vacuum hose/tubing that is broken or unhooked... if no luck seek a mechanic... to find this vacuum leak for you!.. Defog/defrost is the default setting for this 'vacuum' controlled system!! Good idea, cause you may need that mode!

Possible mode door actuator replacement.