As I stated before, you are the only one with the immediate feedback who can make the decision when to start back. If your body is telling you "no" then wait. I think it's a mistake to just take off a few weeks and start running. Try walking first.
Why the obsession with "base"? Why 100 miles a week? You're running 800 meters aren't you? Why have you talked yourself into believing you'll be "mediocre"? Quit listening your your friend, he doesn't know what he's talking about. When I was in high school I basically didn't do squat until February (Sr) or March (So and Jr). You are at the age where you'll improve just because your body is maturing with each passing month.
If you really understood what SOM means you'd understand that starting out in March is just fine. You do realize that you can start running track workouts that are aerobic, don't you? You do realize that you can make dramatic improvements in a manner of weeks if you're patient?
I think some of you guys have trapped yourself into some fantasy that you need to "get base" then go to some next step, as if it was a sacrosanct progression that can't be broken. "Base" is something that is accumulated over years. "Base" is something that is continually being built. You make want to structure your years in phases, but if you can't, there's nothing lost, just get on with it. Running and life are a lot like a card game - you play the cards that you are dealt, not the ones you'd like to have.
All runners should have the mindset that they are athletes and a competitors first and foremost. They should crave competition, not fabricate ways to avoid it. If you are a competitor first, you'll soon become a runner. Good luck.
Here is a little backgroud as to where SOM came from:
"Summer of Malmo" was born out of John Schiefer's Track&FieldMedia.com message board almost ten years ago. Tranck&FieldMedia was the "Granddaddy of the running message boards" and had Schiefer not decided to spend more time on his day job Letsrun would have never become the "world famous message board" it is today.
Track&FieldMedia.com was just like it is here today, full of runners looking for the secret workout or the secret program that will take them to the next step. Every year about this time they start devising all sort of ingenious plans for the Summer to get them ready for cross country season. Then, as it is now, they were looking for a blueprint for the Summer, when in reality there is no blueprint, there are no secret workouts at all. All there is, is consistency, persistence and patience -- just as it always was. Summer of Malmo is a concept, not a blueprint, not a plan and certainly not a system. What it is, is all things to all runners, I guarantee it. Feel free to adjust it to suit your needs.
Knowing that "consistency, persistence and patience" doesn't excite anyone, one day I posted on T&FMedia.com that I had the Summer program that was exactly what all of the young bucks were looking for, and that when I get a chance I'll post it. This became somewhat of a running joke at the T&FMedia message boards, each week someone would ask about my summer "training" program and each week I's say, I'm still "working on it.
Finally in June, I realized I couldn't procrastinate any longer, so I sat down and wrote "Summer of Malmo" with the Seinfeld episode of "Summer of George" in the background on TV. It was born part out of reality, the Summer of 1989 that Terrance Mahon decided he was going to get serious, and went from unknown scrub to College All-America, but it was also part reflection of mine as to how high school and college runners should go about training during the Summer months between seasons.
Historically, runners tend to come from two camps; their motivation gets misplaced during the Summer and they do too little training to prepare themselves for XC, or they train too hard, come to school in great shape and don't improve, causing disillusionment and misplaced blame on their coaches for ruining them.
I decided that if I could do it over again, or if I were a college coach, I'd direct my runners that the first thing they should do when they get home from school after the Spring semester is to call all of their old running friends up and make a commitment to meet twice weekly for informal training sessions. I'd tell them to put the word out to all of the local high school teams and invite them to the training sessions as well. The point of those sessions would be that this is a social event and the workouts would be low-stress aerobic training. All workouts would be run at an intensity level that is well within their abilities.
The idea of having runners all run the same pace, periodically jumping in and out of the workout that the lead group is doing, also came out of that Summer of 1989. I had been knocked out of training by a dose of sciatica. When I started running, I decided that rather than building up my mileage with all easy runs, I'd start doing interval work on the track immediately, but I'd start off running slow and short, gradually lengthening the distance and increasing the speed as my body let me. The original "Summer of Terrance" group consisted of Terrance Mahon, Peter Fonseca, Brad Hudson, Colin Dalton and myself, with assorted guest stars jumping in (not sure how many times Pat Haller made it) depending on who was in town for that session. There were times that I'd jump in for a lap (while the group was running a 5 mile tempo run) then wait until they got back around, then I'd jump in again, and so on. Each week I'd run a little bit more and/or a little bit faster, finally by the end of the Summer I caught up to the leaders. This was the easiest Summer of good training I ever had.