Most listings are in the $30's per square foot per year. The Altadena region is going through a a boost in rates. In the last 3 months, the median rate increased $31 per sqft per year.
Compared to the rest of the Metropolitan Los Angeles market, the Altadena region has lower rates, so you should have no trouble finding a great deal in this depreciated region.
In the last 90 days, 0 listings have come on the market, which means new availabilities most likley are going fast. You'll want to be prepared to make an offer immediately. About NaN% of the available leases in the Altadena are subleases, so you will probably need to sign a longer term lease with the landlord directly. There aren't many listings below 2,000 square feet available, so finding a space for a small business might be tough.
Even though the median size is 33,990 sqft, there are still 0 leases below 2,000 sqft. Most properties in this region are around 1 floors. Most buildings in this market were built in 1946 and are Class A.