I guess it would depend on what you wanted to make, or the reason you want to do a lager. There are a few options you have in my opinion.
If 68 degrees is your room temp, you can sometimes get a 10degree drop in temp by placing the carboy in a tub of water with a shirt covering the carboy and the bottom of the shirt soaking in the water. You could get as low as 60 or 58 degrees. Cool enough for some lager yeast.
You could do a Kolsh style beer that is an Ale, but you ferment the secondary at colder temps and some people ferment the primary with an ale yeast, and add Lager yeast to the secondary. I just use White Labs Kolsh Yeast.
You could do a cream ale. This style can use either type of yeast from what I have read. But I have never made one so my experience in it is limited.
Or you could just experiment with what you feel is best. You never know, you could make something that blows you away, and seems to break the conventional "rules" of brewing. It would be a specialty beer.
The Lager yeast will ferment at the higher temps but you will get some off flavors, and the ale yeast can ferment at the slightly cooler temps, but will take forever.
I know this didn't help much, but I just wanted to offer my opinion.