The western Darién is fairly accessible by road from Panama City [1]. The Lago Bayano [2] area is particularly easy to get to, and it’s now also possible to drive north across the western Darién all the way to Kuna Yala [3].
Most people heading farther east than that prefer to fly.
However, travelers with more time than money can get to La Palma [4], El Real [5], and parts of Parque Nacional Darién [6] by road and boat [7].
Links:
[1] http://www.moon.com/destinations/panama/panama-city
[2] http://www.moon.com/destinations/panama/the-darien/western-and-central-darien/lago-bayano
[3] http://www.moon.com/destinations/panama/kuna-yala
[4] http://www.moon.com/destinations/panama/the-darien/coastal-and-upriver-darien/la-palma
[5] http://www.moon.com/destinations/panama/the-darien/western-and-central-darien/el-real-de-santa-maria
[6] http://www.moon.com/destinations/panama/the-darien/parque-nacional-darien
[7] http://www.moon.com/destinations/panama/the-darien/darien-river-adventures