From Lower Merion, you are not far from lots of beautiful roads. Depending on how much time you can spare, your best bet, I think, is to find a local club ride to join. Check out the following clubs:

1. Suburban Cyclists Unlimited:
http://www.suburbancyclists.org/

2. Central Bucks Bike Club:
http://www.cbbikeclub.org/?body=ridelist&nav=rides

3. Bike Club of Philadelphia:
http://phillybikeclub.org/newbcp/rides/calendar

4. Delaware Valley Bike Club:
http://www.dvbc.org/rides/calendar/f...h=11&Year=2008

The Trail, a simple up and back route, is not particularly scenic or challenging; I suggest doing it only if you can't find a suitable road ride with one of the local clubs. BCP, SCU and CBBC each have large cue sheet libraries, but a cue sheet won't be of much use if you don't know the territory. The further you get from suburban congestion around Philadelphia, the riding gets better, so head north or west of Lower Merion. (East is good too but less convenient from Lower Merion.)