My daughter is single and wants to adopt an infant or a small child how good are her chances of this happening?

If there's not any significant reasons for her not to have a child then yes

Actually they are not that great. There are too many couples waiting to adopt that will be given preference.

Her best bet is with an older, special needs child.

Most birthmothers feel that if they're going to even THINK about having their child raised by a single parent, they'd do it themselves.

Part of the main draw of adoption for birthparents is the idea of a family--not of a single parent.

Your daughter is better off, as stated, looking for an older or special needs child.

Her OTHER option, which would generally also have her with older or special needs children, is to become a foster parent.

Here is a list of single parent adoption support sites that might be helpful
single parent adopting - Yahoo! Search Results

Depending on which state you/she is in (its not allowed in some states from what I understand) she can find/hire a surrogate mother willing to give her child to her.

Thanks for all your advice