Can you have an acl injury without major problems walking?

Absolutely: After the initial acl tear, your knee can function quite normally as long as you don't attempt to twist your knee on a planted foot (cutting motions moving side to side such as during sports activities). Walking and running doesn't typically require a functioning acl. Many people that don't participate in cutting activities do quite well without an acl.

Yes: Acl injury affects different people to different degrees. A partial or even a complete tear might not result in difficulty doing low impact, non-pivoting activities once initial swelling and pain resolves. Twisting or lateral agility or jumping and landing activities would be more difficult and might cause instability or "giving way". A doctors exam or an MRI could confirm the diagnosis.