The California Assn. of Realtors said its index--which measures how many households can afford the median-price home--reached a seven-year high in February, rising to 36% from 33% in January. A year ago, it stood at 32%. The group said the February median price dipped 1% to $125,327, although it stood 1.8% higher than in February, 1986. Median price means that half the homes sold for more and half for less.