ACA is definitely a great resource for rides and they run plenty of 'em out of the north side of Austin...I think both Saturdays and Sundays.

Parmer Lane is probably one of the more popular rides up north...it has a super-wide breakdown/bike lane and you can do 70 mile out-and-backs if you're so inclined. A new Bicycle Sport Shop opened a location on Parmer last year, so they might be a good resource for you too. The Liberty Hill area also has a lot of nice cycling...a couple of the popular organized rides each year begin out of there.

There are plenty of country roads to explore...which usually have low traffic...but a lot of 'em don't have bike lines or any space to the right of the white line...and sometimes they are 55 mph speed limits so it can get a little hairy.

I live just west of downtown and spend a lot of time on 360/Bee Caves Road/620...and while traffic is fairly heavy and fast, the 12 foot shoulders provide me a level of comfort.

I've ridden Parmer several times and it's a good workout...the further away from town you get, the fewer options for water (important on those 95-degree days).

Bennie222 is from RR and probably has some suggestions also...if he doesn't find this you might want to PM him.