Why not just try it out 
?
But AFAIK Spark.connect() does not block forever - at least this was my experience on the Core.
Have a look here: Create time out for Spark.connect()?
On the other hand if it does block, you can still use the code of above post to cancel a connection attempt.
Just be aware, that - on the Photon - SparkIntervalTimer library is not yet working (properly) and that Spark.connect() does/did not implicitly perform a WiFi.connect() - as reported by some users.