I am to take 50, 000 iu of vitamin d (my level is 26.7) once a week. Could I take one capsule every other week and still benefit?

Yes. With that level, you will still get the benefit, but it will take your vitamin d storage a little longer to build up. Vitamin d is fat soluble, which means that our body will continue to store it. Levels can easily be assessed with blood testing.
Will take longer. A low level of vitamin d means that the body as a whole is low, including the fat cells that store vitamin d. Just taking a normal daily amount won't bring the fat stores up to normal levels, so a high dose capsule is used to catch up. Since there is a certain amount of vitamin d needed to do this, taking a capsule every other week means it will take twice as long to get caught up.
Vitamin D deficiency. First, you should know that the institue of medicine and the national endocrinology group have lowered the threshold level for determining vitamin d deficiency from 30 ng/ml to 20 ng/ml, thus your current level would now be considered in the normal range. Taking the vitamin d 50, 000 every other week would be effective, but over time would carry a risk of achieving excessive vitamin d levels.