Where to eat tomorrow night alone..staying on the outskirts of oldtown.
Wine Vault, definitely. They do a prix fixe menu on Fridays but it is actually fairly cheap and you can add on a wine flight for $15.
If you take a cab, tell the driver it is near Shakespeare's Pub at the Washington St & I5.
Signage is difficult, it is above the street sandwiched between the Pub and a few other places (Saffron)
Mission Valley per se does not have much great food,
-Other than the new (and with long lines): http://www.truefoodkitchen.com/
-I personally like the old: http://www.neimanmarcus.com/stores/store.jsp?storeId=16/SD&rest=200039&_requestid=33374
-Closer to you, on the SW edge of Old Town (and my choice if I was staying right there): http://www.25fortybistro.com/
-More South from Old Town: http://www.winevaultbistro.com/