Hi! That pace seems pretty good on a flat road. For comparison, right after I got my bike I averaged about 11 mph on an 8-mile stretch. Keep at it!! You'll see yourself improve drastically with a regular routine. I was using that route to get to a neighborhood that contains my climbing training routine and I realized I was going 18 mph down that same stretch! I've only been seriously cycling for a month and a half.
As for pedals, I just bought KeO Sprint pedals and Specialized BG Sport shoes(
http://www.specialized.com/bc/SBCEqProduct.jsp?spid=26151). The shoe fits great but I can't comment on how well everything works since they're not installed yet.
I'll post back on Friday when I get them hooked up.