Past usage of marijuana does not exclude someone from enlisting in the military. I would not suggest lying to a recruiter on any subject, as that would lead you to be removed from the military if the lie is ever discovered. Don't do it again, and talk to your local recruiter for more information. Below is an excerpt from AFI 36-2002 with the exact wording:
A2.1. Ineligibility Conditions. Applicant is ineligible to enlist when one of the following conditions (refer questionable cases to HQ SAF/DPXFA for paragraphs A2.1.1. - A2.1.5.) exists:
A2.1.1. Intoxicated or under the influence of alcohol or drugs at any time during enlistment processing or has been involved with narcotics, dangerous drugs, diagnosed as an alcoholic or alcohol abuser
or who self-admits to alcoholism or alcohol abuse, or has had a positive Drug and Alcohol Test (DAT). Forward waivers of preservice drug use or involvement for other than marijuana through AFRS channels to HQ AFRS/CC. They will consider waivers only for limited preservice use of amphetamines, barbiturates or unprescribed anabolic androgenic steroid usage. Marijuana usage after signing AF Form 2030, USAF Drug and Alcohol Abuse Certificate, makes the applicant ineligible for enlistment or waiver consideration. A positive DAT renders an applicant ineligible for waiver consideration. An applicant who completes treatment for alcoholism will be considered for waiver after 2
years alcohol free.
This is AF policy, each component will have their own direction, but the AF is generally the strictest service in these regards. Good luck!