How many days of cross training should I do a week?

I have been doing the following:
1. Fitness runs on Monday, Tuesday, Thursday, and Friday. (40-60 minutes comfortable)
2. Strength run on Wednesday. (10-15 minute tempo w/ one mile warm up and cool down)
3. Endurance run on Sunday. (60-90 minutes comfortable)
4. What I call cross training on Saturday (bike or swim for 30 minutes)

Should I be doing more cross training or different kinds of cross training? What has helped to run your fastest times once you got onto the track in the spring? I run the 800m, 1500m, and 3000m, not in any particular order.

Some things to do for cross training…xc?

my xc team has team runs on monday, tuesday, thursday and friday. wednesday is supposed to be a cross training day by ourselves…the coach said some things to do would be biking or swimming, but i don’t have a bike or access to a swimming pool. would it be okay if i ran by myself anyway? or should i do aerobics? any suggestions are appreciated. thanks!!