We will be staying in Santa Margherita but taking day trips mostly south (Portofino, Cinque Terre...) need suggestions for lunch, dinner with good food but reasonable prices.

Also, doea anyone know how long the train ride is from Santa Margherita to Cinque Terre?

You will love Santa Margherita. We stayed there for four days back in 2000. Our favorite restaurant was Il Frantoio, which is a a little bit off the main drag. It's worth looking for (assuming it's still there.)
The train ride from SML to Cinque Terre is under an hour. If I remember correctly, you can catch more frequent trains from Rapallo which is the next town over. You can also take a ferry to Portofino, but I suggest you bring a lot of money with you (Portofino is way overpriced.)

It's been a while since I was in SML, but I enjoyed dinner at Da Baicin so much we ate there twice. You can read my trip report and see my photos of the area at www.travelswithdiane.homestead.com/Italy6.html
We took the train from SML to the farthest town on the Cinque Terre and it took a little over an hour. From there we worked our way back.

We had a wonderful dinner at a family run restaurant called Il Nostromo at SML. Address was -Via Del Arco, 6. The gnocchi was to die for.

I second the vote for IL" Nostrmo It is very popular with the locals . try the Frito Misto . CIAO!