the lower Deschutes can be reached by going through the gorge or go over hood on 26 to Maupin, to get to the metolius you have to go farther south toward Mt Jefferson. If you only have a day you are going to have to pick one or the other. best bet is to call to see what is active for the hatch and if it is stonefly the hit the Deschutes. the Deschutes is best accessed by drifting but there are locations where you can fish from the bank just be careful the footing can be treacherous. (do your internet recon)
be prepared for colder water temps due to elevation, insulated waders are nice in the spring and necessary if steel heading in the winter.
there is too much to do in one day so try to focus on that one thing you want to do.
If you like micro brew beer and coffee and fresh seafood your are going to a great place. One place to stop for dining, beer, etc and it is close to the airport and sits at the mouth of the Sandy river is a place called the edgefield and it is in the city of troutdale which is at the mouth of the Columbia gorge.
Enjoy your visit and good luck fishing.
P.S.
If you think you will do this on a regular basis recommend picking up the fishing Oregon guide, good book of sites to fish across Oregon with directions on how to get there. I used it to find lakes in the cascades around hood and south to hike in and fly fish from a float tube, and it also helped me find places to fish on the Deschutes.