Yugoslavia did allow its own people to travel to and work in the West from 1960s. It was also a popular tourist destination for both Western (eg. West German) and Eastern (eg. Polish and Czech) people. However, it was not widely used as a transit point for those from the East that would want to cross to the West. I'm not exactly sure how or why, but would guess that there would be limits on people with East European passport crossing Yugoslav western borders.

For example, during and after Prague spring, many Czechs that were on vacation in Yugoslavia at the time were offered longer term lodging and hospitality (partly through popular sympathy, partly to support what was seen as Titoist-like initiative). However, most eventually returned to Czechoslovakia, rather than continue on to the West. Again, I'm not sure what the mechanism was, seeing as at the time Yugoslavs could freely travel to the West.

As for the Iron Curtain, it was on neither or rather both sides. Before 1948 and Tito-Stalin split it was firmly on the Soviet side, but eager to preserve its independence within state socialist context. After the split, and before destalinisation and restoration of relations with USSR in mid 50s, it gravitated more to the West, but kept the socialist system. After that, it sort of kept the balance, trading with both sides, while preserving both its independence and socialism.