There is no way for anyone wo know if you will be able to pass on the first go around. You would be the best judge of that really. I got mine on the first try just using the Lamale and Cisco study guides and some routers to play around with.
You will have to judge when you know the material well enough to pass. Take the practice tests over and over. Mix up the questions, and when you are able to get like 90% on every exam then you are probably ready.