I am using  google adwords service for promoting my site and  I need some advice about budget.  Is it a good idea to let Google optimize your budget?
Regards,

i would start with a very very low budget...

then tweak, tweak, tweak your ads some more until you are getting the results and ROI you want

only at that point look to raise your budget

theres a ton of ebook, manuals, etc on the subjest of adsense and how to best use it - run a simple search and you'll find plenty of info

I would also highly recommend setting up specific goals and tracking how much it costs to reach your goal.  If you are selling a product, you can track how much it cost to sell each product.  If you are doing free registrations (like a forum) you can track how much each new registration is costing you.

There is simply no replacement for identifying how much advertising is costing you in a real cost/benefit analysis.  Fortunately both Adwords and Analytics offers easy implementation of tracking.

I agree with Nic, start very low i have a site am running adwords and google was suggesting $80+ daily for my campaigns of which i thought was a bit high especially since i am just starting off in adwords i am managing my daily budget to $10 daily per campaign with 3 campaigns running and am satisfied with the performance. I even have one with a $5 daily budget and doing well but have bid highly on several keywords.

Monitor the ads and identify the best performing and do away with the ones performing poorly - as Nic said tweak, tweak, ......

You might want to check here for some good articles on adwords which i found useful recently.

All the best
Kwezi