Here is my usual breakdown, so you are not really so far behind
Cross 2 sec
F2L 8 sec
OLL 2 sec
PLL 3 sec
Total 15
Looks like you need to work on your LL more than anything to get under 20. Yes, it is great practise to solve the cross blindfolded, and you just have to learn to not follow the pieces, it will come with experience. Also make sure you only have a max 15 secs inspection, and that yoiu don't look at the cube between putting it down, and picking it up again (maybe look for one sec before picking up) to simulate a competition condition.
Dan