Medical marijuana advocates in California's high tech Silicon Valley are furious over what they interpret as a demand for a "barter" system for transactions at pot dispensaries in San Jose. The city, which is brimming with nearly 70 pot shops, is considering a proposal to cap the number of dispensaries at 10 and ask local voters to approve a 3 percent tax on pot businesses per $1,000 in gross receipts. But an organization representing numerous dispensaries is particularly irked by language in a city staff memorandum suggesting that no cash sales are allowed at pot shops.