University Ave is a good place to start, with University Cafe possibly the quintessential startup/VC coffee heaven. The paper tableclothes are perfect for sketching out your latest startup plan! Coupa Cafe, just off University Ave, is also pretty vibrant. Further south in Palo Alto, in the city's "second downtown" on California (near ECR & Page Mill) you'll find Printer's Cafe. Good coffee, wifi, but a much quieter place.