Hi and welcome to Just Answer!
The recruiter was correct that Hong Kong taxes are relatively low - with maximum tax rate on wages - 20% (compare with 35% in the US) and temporary was reduced to 17% - http://www.ird.gov.hk/eng/pdf/pam61e.pdf
You can estimate your annual Hong Kong taxes using this calculator - http://www.guidemehongkong.com/taxation/topics/hong-kong-tax-calculator
As US citizen - you are required to report all your worldwide income, but because you will be living abroad - you might be entitled for a foreign earned income exclusion. That exclusion is not granted automatically - you need to file your tax return to get it.
For the person to qualify for the foreign earned income exclusion - he/she should: -- Work and reside outside the United States for at least 330 days during the year(Physical Presence test), or -- Meet either the Bona Fide test.If the person qualifies, he/she may exclude up to $91,500 (in 2010) in foreign wages -- plus housing allowances. Here are forms you likely need: Form 2555 Instruction 2555
Please also see for reference this publication - www.irs.gov/pub/irs-pdf/p54.pdf
Let me know if you need any help or clarification.