how many people live on the islands

Joshua, please look at the top of the VINOW site and you'll see lots of facts, statistics, etc. about all of the USVI including population.

...and in the Moving Guide stat section, it states:

124,778 (2003 est.)

For what it's worth...

Population of Territory: 108,612 (2000)*

Population of Territory by Island*
St. Croix: 53,234
St. Thomas: 51,181
St. John: 4,197
Water Island: 161

St. Croix: Population Breakdown by Area*
Christiansted town: 2,637
Frederiksted town: 732
Anna's Hope: 4,192
Christiansted (Sub-district): 2,865
East End: 2,341
Frederiksted (Sub-district): 3,767
North Central: 5,760
Northwest: 4,919
Sion Farm: 13,565
South Central: 8,125
Southwest: 7,700

St. Thomas: Population Breakdown by Area*
Charlotte Amalie (Town): 11,004
Charlotte Amalie (Sub-district): 18,914
East End: 7,672
North Side: 8,712
South Side: 5,467
Tutu: 8,197
West End: 2,058

St. John: Population Breakdown by Area*
Central: 746
Coral Bay: 649
Cruz Bay: 2,743
East End: 59