Unfortunately as much as some people don't want to hear the bad news, they are there so you can be prepare for it. So don't blame ppl if they sounded negative, everybody in the US are frustrated with the whole economy thing and you know it's not getting better anytime soon.
I've been in the US for almost 2 years in April, and I got laid off 6 months ago from a very good job working for top 15 company in the US. So if you want honest answer to your questions, expect 6-12 mths (or more) of full-on job hunting and this depending greatly on which states you are planning to stay.
Myself, took me 5 full months of job searching before I got another full time job.
Also I'm afraid the type of jobs that you are after will determine how fast you can get a job too. Finance, retails, design architecture, building/house developers, hotelier/hospitality are some of the dead jobs right now. Technology side also cutting people but depending on your skills, you may still be able to get a good job.
If you are not too picky in your first year in America, you will still be able to get some retail or restaurant work until you find your desire role, but expect to get paid minimum wage (differ by states) and some part timers dont get benefits (health insurance, vacation, sick leave), if you are single you will probably can get by, but this is especially tough if you have husband/wife and kids to feed.
I would say, save as much as money as you can. Try to look for jobs before you get here to have some kind of ideas (market and money wise). Be prepare to cold calling companies and directly hand out your resumes if you have to and get rejected at the same times. Your persistent will pay off but you just have to be patient at this point. My close friend got laid off from his 100K job. It has been 7 months, and he can't even get a job at Starbucks. This is not a scare tactic, but you will compete with hundreds other for one good job and they are all qualified just like you.
Good luck!