If you were on the west coast, you would be trained at Marine Corps Base San Diego. If you were on the east coast, you would go to the Marine Barracks at Parris Island, South Carolina. About 200,000 Marines were trained at each of these two sites. African-American Marines were inevitably segregated, and went to Montford Point, at Camp Lejeune, North Carolina.

Initially, before the war, recruit training was eight weeks long. In September of 1939 a state of emergency was declared and it was shortened drastically to four weeks. The Marine Corps realized this was not long enough and changed it to six weeks in January 1940. Until February 1944 when a modified eight-week schedule was adopted by both depots, training varied in length from five to seven weeks.

Here's the prewar eight week schedule:

• Indoctrination and Military Courtesy: 7 hours
• Bayonet Training: 5 hours
• Close Order Drill: 41 hours
• Field Training; 34 hours
• Interior Guard: 6 hours
• Marches: 16 hours
• Rifle Range: 70 hours

This is a mid-war schedule at San Diego used in 1943 that was seven weeks long:

• Weapons training: 138 hours
• Physical fitness training: 14 hours
• Garrison instruction: 62 hours
• Field training: 57 hours

And finally the last type of schedule, mandated in February 1944. In July 1944, 36 additional hours of weapons training was added. The increase is not shown here:

• Weapons training: 195 hours
• Physical fitness training: 39 hours
• Garrison instruction: 89 hours
• Field training: 98 hours

You can see how the Corps streamlined the training schedule because of the war.

Sources:

Marine Corps Ground Training in World War II, by Kenneth Condit, Gerald Diamond, and Edwin Turnbladh. Government Printing Office, 1947.