This is applicable to each individual because it identifies the subject of the instruction as "he", ie the individual who responds to the Gospel either positively or negatively.
Here, the subject is "them", ie plural, and refers to general signs following the church (them that believe). This passage does not seem to be applicable to each individual believer, but rather is descriptive of the general character of the community of the saints, indicating that they would have miraculous or supernatural signs attending them (as a community). So the initial evidence doctrine is not based just upon this passage, and I would not use this passage as a proof of initial evidence doctrine for each believer, but instead would use it as a proof of the general character of the true Christian church. Thus, a church that has nobody speaking in tongues, nobody casting out demons, nobody taking up serpents, or drinking poison without ill effects, or ministering divine healing, is most likely not a church of genuine believers.
I would also point out that each of the signs listed is circumstance - dependent. Meaning, demons aren't cast out unless there are demons to be cast out, sick folks aren't healed unless there are sick folks to be healed, serpents aren't picked up unless there are serpents that need to be picked up, and so on and so forth. And this applies to speaking in tongues as well, as
1 Corinthians 12-14 shows there is a time and place for speaking in tongues, and a time and place for NOT speaking in tongues.
Initial evidence, however, is based upon Joel's prophecy, Moses' stated desire (which can be understood as a prophecy), and the inspired interpretation of Joel's prophecy as given by Peter in
Acts 2.