You can go alone at Shivapuri. Some footpaths at Shivapuri connect village and temples so there are people walking around(but not too many, very friendly). We went there by taxi in 2007 without a guide. Security is fine as this place is managed by the army. Bringing your lunch or you could ask for simple food at temples.
I don't know much about the other two places but advice was given not to go there as the security condition was not good at that time. Check the info at the bird forum net and OB e-group.
Good luck
Captain
