股市嘅「好友」同「淡友」英文點叫？

There is no such thing as 好友 and 淡友 in English as far as my understanding.

In the western investment world, people tend to use the following "market long" and "market short", this is a good indication of whether the market is net long or short, you can find this information at the HK Exchange website.
http://www.hkex.com.hk/data/futuresdata/sharedata.htm

They would also use the "Investor Confidence Index" to measure the attitude of investor to risk. For example the State Street Investor Confidence Index (http://www.statestreet.com/industry_insights/investor_confidence_index/ici_overview.html)

Aside from the above, they will also monitor the institutional investor money movement as general public investors tend to have less impact to the market movement.

Hope this help

Cheers