Having taken the course and looking at your background, I say go for it. It's good you have the programming background. Some people wonder if they have enough and not everyone likes looking at code. To answer some questions:
Is there any measurement if Im good enough to take OSCP course ?I would read some of the PWB Reviews. A lot of them have listed the individual's background listed off. If the review is on a Security Related blog, you can get a feeling of the persons background prior to them signing up for the course. We also have on here a lot of reviews. Search, search, search!
2. Can I start course every month or there is some period ( I read that 16th march is deadline in this month) ?At the time I enrolled for PWB v3, they were accepting new students every week. Enrollment will continually be available - it's just a matter of picking a time that best fits your schedule.
3. Is there any more knowledge that I need to have before taking course?I agree with what MaXe mentioned. Having that basic networking knowledge and being comfortable in a shell will always help. This isn't a course where you point and click to own boxes.
4. The certification itself is it good on today job market?It's picking up more and more. Here's a quick Dice listing after searching 'OSCP':
http://www.dice.com/job/results?caller=basic&q=OSCP - Yields 16 results currently. I'll tell you that after searching dice for that keyword a couple years ago, you would be lucky to pull back > 5 jobs. It's great to see it getting well deserved recognition.
One more question :
Is it better to take 1 month labs and if I need more time than buy additional time or it is better to take straight 3 months from the start?
I'd say go with 60 days at least. If you do 90 days from the start, your mainly saving money. If you need more lab time after your time expires, your always welcome to purchase more time. Know that Lab Time is valuable. There's a good amount of vulnerable systems sitting out there across multiple subnets. I know OffSec has expanded the labs since I took the course. Be sure to purchase enough lab time according to how much time you can commit.
Though g0tm1lk says if you want to just pass do 30 days, I would advise against it. It's obvious with his blog that he is rather comfortable in BackTrack, and had a lot of time to spend in the Lab. Perhaps 30 days would of been OK for Version 1 and 2 of the course, but again I highly emphasize at least 60.
Lastly, your going to have a blast in the course! Were all here for you if you need anymore advice.