PTW has Great Selection of Activities To Meet Other People
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I stayed at Pacific Tradewinds for a week whilst I was in San Francisco - I was there for business (4-day conference) but had extra days to explore the city which is what made me choose PT. I had a great group cycle to Sausalito and met some lovely folks from all over the world. I literally only used this hostel for a place to sleep and was out on my own for the trip (through choice, apart from the bike ride) but the hostel put on a great selection of activities for you to meet other people.