\documentclass[english,french]{article}
\usepackage{babel}
\addto\extrasfrench{%
   \providecommand{\og}{\leavevmode\flqq~}
   \providecommand{\fg}{\ifdim\lastskip>\z@\unskip\fi~\frqq}
}

\begin{document}
\selectlanguage{english}%
word\foreignlanguage{french}{ in English at a paragraph start}
\end{document}
