Your preamble shows that you use the float package. When you use the float package, the correct placement parameter for right here is H. So write your table like this in the Org mode file:
#+ATTR_LATEX: :placement [H]
#+CAPTION: My Table
| a | b |
| 1 | 1 |
| 2 | 4 |
| 3 | 9 |
| .. | ... |
Without the float package, @mankoff's ...
Try adding #+ATTR_LATEX: :placement [!h] as a header to the table. That says: Place the table here. The trouble with it is that if the table doesn't fit here, you'll end up with lots of blank space and the table on the next page.
Alternatively, \clearpage at the end of a section forces all floats (tables, figures) to be placed.