Hello.

Well I feel that you should try for CSE as it is the area of your interest and you can do wonders when you get to study about something that you are interested in. If you study mechanical without having interest in it, things will become hard for you as you won't be able to give the required dedication. Soon there will be chances of getting frustrated and there will reach a point when you will be doing things for the sake of doing it, without any passion at all.

Now if you don't want to take the risk of waiting for a seat in CSE branch, you can always opt for a stream change in the 2nd year of your college. For this though you will have to get above a required cutoff ygpa in your first year examination.

Now it's your call.

Hope that helped.