Duathlete in Training

I'm going to start training for my first sprint duathlon soon, within the next 2 weeks. Training for my first marathon is scheduled for June, but I need an intermediate goal to keep me motivated and fit until then. My target race is on 7/28 at Baldwin Park, but we'll see how things go (I have my eye on ones sooner if I feel ready before June).

I mainly want to do a duathlon because I need a new challenge, but also because biking is the necessary cross training I need to avoid injury for my long distance running (since I suck at strength training). Since I'm going to be biking regularly anyway, I may as well put it towards a goal. And I can't very well let Jason show me up with his triathlon too much, can I? =P
 
So anyone out there have duathlon experience and care to share your training tips or advice as I embark in this new crazyness? 

Here is my plan so far (which is still a gooey mess and not at all set in stone):

• The distance of the sprint duathlon is 5k - 13.4 - 2.5 (seem like really odd distances to me).

• Every weekend (or so, to accomodate races as needed) I'll start doing run-bike-run workouts starting with short distances of 1-3-1 and add to one leg each week slowly. 

• Maybe I'll keep the runs to 1 mile at first and increase the bike distance by a mile each week until I've reach 1/2 the distance of the race, then start increasing the runs by 1/2 a mile one at a time each week.
  
  
• Or should I leave the runs at 1 mile until I cover the full bike distance and then add to them at the end since I need to work on increasing cycling speed more than the running?
  
  
• I'm thinking these would replace my weekend long runs, but that might be ok because I probably won't be racing anything longer than 5Ks until then.
  

• Additional weekly workouts:
  

• bike to work with Jason and Amy at least once a week (30-32 miles roundtrip), eventually working up to twice a week. (We did a test run this weekend, which solidified my desire to try a duathlon. I'll post a separate blog post about that later.)
  
  
• run 2 days a week for 2-3 miles each.
  
  
• run a 5K race every 3-4 weeks.
  
  
• cross training: yoga, kickboxing, abs
  
  
• bring my bike to work for transportation between my office and campus for meetings and to get to other workouts at the gym. These would be short bike rides of about 2 miles each way.
  
  
• bike or walk whenever feasible to run errands, to events, and to workouts.
  

Thoughts?